--- a/#symbolics.rst#	Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,343 +0,0 @@
-Symbolics with Sage
--------------------
-
-Hello friends and welcome to this tutorial on symbolics with sage.
-
-
-.. #[Madhu: Sounds more or less like an ad!]
-
-{{{ Part of Notebook with title }}}
-
-.. #[Madhu: Please make your instructions, instructional. While
-     recording if I have to read this, think what you are actually
-     meaning it will take a lot of time]
-
-We would be using simple mathematical functions on the sage notebook
-for this tutorial.
-
-.. #[Madhu: What is this line doing here. I don't see much use of it]
-
-During the course of the tutorial we will learn
-
-{{{ Part of Notebook with outline }}}
-
-To define symbolic expressions in sage.  Use built-in costants and
-function. Integration, differentiation using sage. Defining
-matrices. Defining Symbolic functions. Simplifying and solving
-symbolic expressions and functions.
-
-.. #[Nishanth]: The formatting is all messed up
-                First fix the formatting and compile the rst
-                The I shall review
-.. #[Madhu: Please make the above items full english sentences, not
-     the slides like points. The person recording should be able to
-     read your script as is. It can read something like "we will learn
-     how to define symbolic expressions in Sage, using built-in ..."]
-
-Using sage we can perform mathematical operations on symbols.
-
-.. #[Madhu: Same mistake with period symbols! Please get the
-     punctuation right. Also you may have to rephrase the above
-     sentence as "We can use Sage to perform sybmolic mathematical
-     operations" or such]
-
-On the sage notebook type::
-   
-    sin(y)
-
-It raises a name error saying that y is not defined. But in sage we
-can declare y as a symbol using var function.
-
-.. #[Madhu: But is not required]
-::
-    var('y')
-   
-Now if you type::
-
-    sin(y)
-
-    sage simply returns the expression .
-
-.. #[Madhu: Why is this line indented? Also full stop. When will you
-     learn? Yes we can correct you. But corrections are for you to
-     learn. If you don't learn from your mistakes, I don't know what
-     to say]
-
-thus now sage treats sin(y) as a symbolic expression . You can use
-this to do a lot of symbolic maths using sage's built-in constants and
-expressions .
-
-.. #[Madhu: "Thus now"? It sounds like Dus and Nou, i.e 10 and 9 in
-     Hindi! Full stop again. "a lot" doesn't mean anything until you
-     quantify it or give examples.]
-
-Try out
-
-.. #[Madhu: "So let us try" sounds better]
- ::
-   
-   var('x,alpha,y,beta') x^2/alpha^2+y^2/beta^2
- 
-Similarly , we can define many algebraic and trigonometric expressions
-using sage .
-
-.. #[Madhu: comma again. Show some more examples?]
-
-
-Sage also provides a few built-in constants which are commonly used in
-mathematics .
-
-example : pi,e,oo , Function n gives the numerical values of all these
-    constants.
-
-.. #[Madhu: This doesn't sound like scripts. How will I read this
-     while recording. Also if I were recording I would have read your
-     third constant as Oh-Oh i.e. double O. It took me at least 30
-     seconds to figure out it is infinity]
-
-For instance::
-
-   n(e)
-   
-   2.71828182845905
-
-gives numerical value of e.
-
-If you look into the documentation of n by doing
-
-.. #[Madhu: "documentation of the function "n"?]
-
-::
-   n(<Tab>
-
-You will see what all arguments it can take etc .. It will be very
-helpful if you look at the documentation of all functions introduced
-
-.. #[Madhu: What does etc .. mean in a script?]
-
-Also we can define the no of digits we wish to use in the numerical
-value . For this we have to pass an argument digits.  Type
-
-.. #[Madhu: "no of digits"? Also "We wish to obtain" than "we wish to
-     use"?]
-::
-
-   n(pi, digits = 10)
-
-Apart from the constants sage also has a lot of builtin functions like
-sin,cos,sinh,cosh,log,factorial,gamma,exp,arcsin,arccos,arctan etc ...
-lets try some out on the sage notebook.
-
-.. #[Madhu: Here "a lot" makes sense]
-::
-     
-   sin(pi/2)
-   
-   arctan(oo)
-     
-   log(e,e)
-
-
-Given that we have defined variables like x,y etc .. , We can define
-an arbitrary function with desired name in the following way.::
-
-       var('x') function(<tab> {{{ Just to show the documentation
-       extend this line }}} function('f',x)
-
-.. #[Madhu: What will the person recording show in the documentation
-     without a script for it? Please don't assume recorder can cook up
-     things while recording. It is impractical]
-
-Here f is the name of the function and x is the independent variable .
-Now we can define f(x) to be ::
-
-     f(x) = x/2 + sin(x)
-
-Evaluating this function f for the value x=pi returns pi/2.::
-	   
-	   f(pi)
-
-We can also define functions that are not continuous but defined
-piecewise.  We will be using a function which is a parabola between 0
-to 1 and a constant from 1 to 2 .  type the following as given on the
-screen
-
-.. #[Madhu: Instead of "We will be using ..." how about "Let us define
-     a function ..."]
-::
-      
-
-      var('x') h(x)=x^2 g(x)=1 f=Piecewise(<Tab> {{{ Just to show the
-      documentation extend this line }}}
-      f=Piecewise([[(0,1),h(x)],[(1,2),g(x)]],x) f
-
-Checking f at 0.4, 1.4 and 3 :: f(0.4) f(1.4) f(3)
-
-.. #[Madhu: Again this doesn't sound like a script]
-
-for f(3) it raises a value not defined in domain error .
-
-
-Apart from operations on expressions and functions one can also use
-them for series .
-
-.. #[Madhu: I am not able to understand this line. "Use them as
-.. series". Use what as series?]
-
-We first define a function f(n) in the way discussed above.::
-
-   var('n') function('f', n)
-
-.. #[Madhu: Shouldn't this be on 2 separate lines?]
-
-To sum the function for a range of discrete values of n, we use the
-sage function sum.
-
-For a convergent series , f(n)=1/n^2 we can say ::
-   
-   var('n') function('f', n)
-
-   f(n) = 1/n^2
-
-   sum(f(n), n, 1, oo)
-
-For the famous Madhava series :: var('n') function('f', n)
-
-.. #[Madhu: What is this? your double colon says it must be code block
-     but where is the indentation and other things. How will the
-     recorder know about it?]
-
-    f(n) = (-1)^(n-1)*1/(2*n - 1)
-
-This series converges to pi/4. It was used by ancient Indians to
-interpret pi.
-
-.. #[Madhu: I am losing the context. Please add something to bring
-     this thing to the context]
-
-For a divergent series, sum would raise a an error 'Sum is
-divergent' :: 
-	
-	var('n') 
-	function('f', n) 
-	f(n) = 1/n sum(f(n), n,1, oo)
-
-
-
-
-We can perform simple calculus operation using sage
-
-.. #[Madhu: When you switch to irrelevant topics make sure you use
-    some connectors in English like "Moving on let us see how to
-    perform simple calculus operations using Sage" or something like
-    that]
-For example lets try an expression first ::
-
-    diff(x**2+sin(x),x) 2x+cos(x)
-
-The diff function differentiates an expression or a function . Its
-first argument is expression or function and second argument is the
-independent variable .
-
-.. #[Madhu: Full stop, Full stop, Full stop]
-
-We have already tried an expression now lets try a function ::
-
-   f=exp(x^2)+arcsin(x) diff(f(x),x)
-
-To get a higher order differentiation we need to add an extra argument
-for order ::
- 
-   diff(<tab> diff(f(x),x,3)
-
-.. #[Madhu: Please try to be more explicit saying third argument]
-
-in this case it is 3.
-
-
-Just like differentiation of expression you can also integrate them ::
-
-     x = var('x') s = integral(1/(1 + (tan(x))**2),x) s
-
-.. #[Madhu: Two separate lines.]
-
-To find the factors of an expression use the "factor" function
-
-.. #[Madhu: See the diff]
-
-::
-    factor(<tab> y = (x^100 - x^70)*(cos(x)^2 + cos(x)^2*tan(x)^2) f =
-    factor(y)
-
-One can also simplify complicated expression using sage ::
-    f.simplify_full()
-
-This simplifies the expression fully . You can also do simplification
-of just the algebraic part and the trigonometric part ::
-
-    f.simplify_exp() f.simplify_trig()
-    
-.. #[Madhu: Separate lines?]
-
-One can also find roots of an equation by using find_root function::
-
-    phi = var('phi') find_root(cos(phi)==sin(phi),0,pi/2)
-
-.. #[Madhu: Separate lines?]
-
-Lets substitute this solution into the equation and see we were
-correct ::
-
-     var('phi') f(phi)=cos(phi)-sin(phi)
-     root=find_root(f(phi)==0,0,pi/2) f.substitute(phi=root)
-
-.. #[Madhu: Separate lines?]
-
-as we can see the solution is almost equal to zero .
-
-.. #[Madhu: So what?]
-
-We can also define symbolic matrices ::
-
-
-
-   var('a,b,c,d') A=matrix([[a,1,0],[0,b,0],[0,c,d]]) A
-
-.. #[Madhu: Why don't you break the lines?]
-
-Now lets do some of the matrix operations on this matrix
-
-.. #[Madhu: Why don't you break the lines? Also how do you connect
-     this up? Use some transformation keywords in English]
-::
-    A.det() A.inverse()
-
-.. #[Madhu: Why don't you break the lines?]
-
-You can do ::
-    
-    A.<Tab>
-
-To see what all operations are available
-
-.. #[Madhu: Sounds very abrupt]
-
-{{{ Part of the notebook with summary }}}
-
-So in this tutorial we learnt how to
-
-
-We learnt about defining symbolic expression and functions .  
-And some built-in constants and functions .  
-Getting value of built-in constants using n function.  
-Using Tab to see the documentation.  
-Also we learnt how to sum a series using sum function.  
-diff() and integrate() for calculus operations .  
-Finding roots , factors and simplifying expression using find_root(), 
-factor() , simplify_full, simplify_exp , simplify_trig .
-Substituting values in expression using substitute function.
-And finally creating symbolic matrices and performing operation on them .
-
-.. #[Madhu: See what Nishanth is doing. He has written this as
-     points. So easy to read out while recording. You may want to
-     reorganize like that]

--- a/accessing-pieces-arrays/questions.rst	Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,159 +0,0 @@
-Objective Questions
--------------------
-
-.. A mininum of 8 questions here (along with answers)
-
-1. Given the array, ``A = array([12, 15, 18, 21])``, how do we access
-   the element ``18``?
-
-   Answer: ``A[2]``
-
-#. Given the array, ``A = array([12, 15, 18, 21])``, what element is
-   accessed by ``A[1]``
-
-   Answer: ``15``  
-
-#. Given the array, ``A = array([12, 15, 18, 21])``, what element is
-   accessed by ``A[-3]``?
-
-   Answer: ``15``  
-
-#. Given the array, ``A = array([12, 15, 18, 21])``, how do you change
-   the element ``15`` to ``51``?
-
-   Answer: ``A[1] = 51``
-
-#. Given the array, ``A = array([12, 15, 18, 21])``, what is ``A``
-   after the execution of the statement ``A[3] = 24``?
-
-   Answer: ``array([12, 15, 18, 24])``
-
-#. Given the array, ``A = array([12, 15, 18, 21])``, what is the
-   result of the statement, ``A[4] = 24``?
-
-   Answer: IndexError: index out of bounds
-
-#. Given the array, ``B = array([[12, 15], [18, 21]])``, how do we
-   access the element ``18``? 
-
-   Answer: ``A[0, 0]``
-
-#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
-   result of ``B[1]``? 
-
-   Answer:  ``array([18, 21])``
-
-#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
-   result of ``B[1, 1]``?
-
-   Answer:  ``21``
-
-#. Given the array, ``B = array([[12, 15], [18, 21]])``, what element
-   is accessed by ``B[-1, -2]``?
-
-   Answer:  ``18``   
-
-#. Given the array, ``B = array([[12, 15], [18, 21]])``, how do you
-   change the element ``15`` to ``51``?
-
-   Answer:  ``B[0, 1] = 51``   
-
-#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
-   value of B, after executing, ``B[0] = 0``?
-
-   Answer:  ``array([[0, 0], [18, 21]])``   
-
-#. Given the array, 
-   
-   ::
-   
-     B = array([[10, 11, 12, 13],
-                [20, 21, 22, 23],
-                [30, 31, 32, 33],
-                [40, 41, 42, 43]])
-
-   Obtain the elements, ``[[21, 22], [32, 32]]``
-
-   Answer:  ``B[1:3, 1:3]``   
-
-#. Given the array, 
-   
-   ::
-   
-     B = array([[10, 11, 12, 13],
-                [20, 21, 22, 23],
-                [30, 31, 32, 33],
-                [40, 41, 42, 43]])
-
-   Obtain the elements, ``[[10, 13], [30, 33]]``
-
-   Answer:  ``B[::2, ::3]``
-
-#. What command is used to read an image file?
-
-   a. imshow
-   #. imread
-   #. imopen
-   #. open
-
-   Answer: ``imread``   
-
-#. If ``P`` is ``array([12, 13, 14, 15])`` then ``P.shape`` gives
-   ``(4, 1)``. True or False?
-
-   Answer: False
-     
-Larger Questions
-----------------
-
-.. A minimum of 2 questions here (along with answers)
-
-1. Given the array, 
-   ::
-   
-     B = array([[10, 11, 12, 13],
-                [20, 21, 22, 23],
-                [30, 31, 32, 33],
-                [40, 41, 42, 43]])
-
-   Change the array to 
-   ::
-   
-     B = array([[10, 11, 10, 11],
-                [20, 21, 20, 21],
-                [10, 11, 10, 11],
-                [20, 21, 20, 21]])
-
-   using slicing and striding. 
-
-   Answer::
-
-     B[:2, 2:] = B[:2, :2]
-     B[2:, :2] = B[:2, :2]
-     B[2:, 2:] = B[:2, :2]
-
-#. Find out how to display a grayscale image with proper colors. Hint,
-   use ``?`` on ``imshow``. 
-   
-   Answer: ``cmap=cm.gray``
-                  
-#. From the image, ``tagore-einstein.png``, 
-   a. show only the face of Einstein. 
-   b. show only the face of Tagore. 
-
-   Hint, use ``imread`` to read the image and ``imshow`` to show the
-   image.  Use ``cm.gray`` as ``cmap`` to display the image properly.   
-
-   Answer:: 
-
-     F = imread('tagore-einstein.png')
-     imshow(F[:210, 20:180], cmap=cm.gray)
-
-     F = imread('tagore-einstein.png')
-     imshow(F[30:300, 320:480], cmap=cm.gray)
-
-.. #[Puneeth: This question contains answer to previous
-.. question. Shouldn't be shown at the same time.]
-
-
-          

--- a/accessing-pieces-arrays/quickref.tex	Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,12 +0,0 @@
-\textbf{Accessing parts of arrays}
-
-\lstinline|C[i-1, j-1]| to access element i, j in C (mxn).
-\lstinline|C[i-1]| to access i^{th} row
-\lstinline|C[:, j-1]| to access j^{th} column
-
-Assigning to accessed elements, changes them. 
-
-\lstinline|A[m:n:o]| accesses the rows from \lstinline|m|
-to \lstinline|n| (excluded) in steps of \lstinline|o|
-
-Similarly, \lstinline|C[m:n:o, p:q:r]|

--- a/accessing-pieces-arrays/script.rst	Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,426 +0,0 @@
-.. Objectives
-.. ----------
-   
-   .. By the end of this tutorial, you will be able to:
-   
-   ..   1. Access and change individual elements of arrays, both one
-   ..   dimensional and multi-dimensional.
-   ..   2. Access and change rows and columns of arrays. 
-   ..   3. Access and change other chunks from an array, using slicing
-   ..   and striding. 
-   ..   4. Read images into arrays and perform processing on them, using
-   ..   simple array manipulations. 
-
-.. Prerequisites
-.. -------------
-
-..   1. getting started with arrays
-
-.. #[anand: internal reviewer not mentioned]     
-.. Author              : Puneeth
-   Internal Reviewer   : 
-   External Reviewer   :
-   Language Reviewer   : Bhanukiran
-   Checklist OK?       : <06-11-2010, Anand,  OK> [2010-10-05]
-
-Script
-------
-
-{{{ Screen shows welcome slide }}}
-
-Welcome to the tutorial on accessing pieces of arrays
-
-{{{ Show the outline for this tutorial }}} 
-
-In this tutorial we shall learn to access individual elements of
-arrays, get rows and columns and other chunks of arrays using
-slicing and striding. 
-
-{{{ switch back to the terminal }}}
-
-As usual, we start IPython, using 
-::
-
-  ipython -pylab 
-
-
-{{ Show the slide with the arrays, A and C }}
-
-Let us have two arrays, A and C, as the sample arrays that we will
-use to work through this tutorial. 
-
-::
-
-  A = array([12, 23, 34, 45, 56])
-
-  C = array([[11, 12, 13, 14, 15],
-             [21, 22, 23, 24, 25],
-             [31, 32, 33, 34, 35],
-             [41, 42, 43, 44, 45],
-             [51, 52, 53, 54, 55]])
-
-Pause the video here and make sure you have the arrays A and C,
-typed in correctly.
-
-{{{ Pause the recording and type the arrays A,C }}}
-
-Let us begin with the most elementary thing, accessing individual
-elements. Also, let us first do it with the one-dimensional array
-A, and then do the same thing with the two-dimensional array. 
-
-To access, the element 34 in A, we say, 
-
-::
-
-  A[2]
-
-A of 2, note that we are using square brackets.
-
-Like lists, indexing starts from 0 in arrays, too. So, 34, the
-third element has the index 2. 
-
-Now, let us access the element 34 from C. To do this, we say
-::
-
-  C[2, 3]
-
-C of 2,3.
-
-34 is in the third row and the fourth column, and since indexing
-begins from zero, the row index is 2 and column index is 3. 
-
-Now, that we have accessed one element of the array, let us change
-it. We shall change the 34 to -34 in both A and C. To do this, we
-simply assign the new value after accessing the element. 
-::
-
-  A[2] = -34
-  C[2, 3] = -34
-
-Now that we have accessed and changed a single element, let us
-access and change more than one element at a time; first rows and
-then columns.
-
-Let us access one row of C, say the third row. We do it by saying, 
-::
-
-  C[2] 
-
-How do we access the last row of C? We could say,
-::
-
-  C[4] 
-
-for the fifth row, or as with lists, use negative indexing and say
-::
-
-  C[-1]
-
-Now, we could change the last row into all zeros, using either 
-::
-
-  C[-1] = [0, 0, 0, 0, 0]
-
-or 
-
-::
-  
-  C[-1] = 0
-
-Now, how do we access one column of C? As with accessing individual
-elements, the column is the second parameter to be specified (after
-the comma). The first parameter, is replaced with a ``:``. This
-specifies that we want all the elements of that dimension, instead of
-just one particular element. We access the third column by
-
-::
-  
-  C[:, 2]
-
-Following is an exercise that you must do. 
-
-{{ show slide containing Question 1}} 
-
-%%1%% Change the last column of C to zeroes. 
-
-Please, pause the video here. Do the exercises and then continue. 
-
-::
-  
-  C[:, -1] = 0
-
-Since A is one dimensional, rows and columns of A don't make much
-sense. It has just one row and 
-::
-
-  A[:] 
-
-gives the whole of A. 
-
-Following is an exercise that you must do. 
-
-{{ show slide containing Question 2}} 
-
-%%2%% Change ``A`` to ``[11, 12, 13, 14, 15]``. 
-
-Please, pause the video here. Do the exercises and then continue. 
-
-To change A, we say
-::
-
-  A[:] = [11, 12, 13, 14, 15]
-
-Now, that we know how to access, rows and columns of an array, we
-shall learn how to access other pieces of an array. For this
-purpose, we will be using image arrays. 
-
-To read an image into an array, we use the ``imread`` command. We
-shall use the image ``squares.png`` present in ``/home/fossee``. We
-shall first navigate to that path in the OS and see what the image
-contains. 
-
-{{{ switch to the browser and show the image }}}
-
-{{{ switch back to the ipython terminal }}}
-
-Let us now read the data in ``squares.png`` into the array ``I``. 
-::
-
-  I = imread('/home/fossee/squares.png')
-
-We can see the contents of the image, using the command
-``imshow``. We say, 
-::
-
-  imshow(I) 
-
-to see what has been read into ``I``. We do not see white and black
-because, ``pylab`` has mapped white and black to different
-colors. This can be changed by using a different colormap. 
-
-To see that ``I`` is really, just an array, we say, 
-::
-
-  I 
-
-at the prompt, and see that an array is displayed. 
-
-To check the dimensions of any array, we can use ``.shape``. We say
-
-::
-
-  I.shape 
-
-to get the dimensions of the image. As we can see, ``squares.png``
-has the dimensions of 300x300. 
-
-Our goal for this part of the tutorial would be to get the
-top-left quadrant of the image. To do this, we need to access, a
-few of the rows and a few of the columns of the array. 
-
-To access, the third column of C, we said, ``C[:, 2]``. Essentially,
-we are accessing all the rows in column three of C. Now, let us
-modify this to access only the first three rows, of column three
-of C. 
-
-We say, 
-::
-
-  C[0:3, 2]
-
-to get the elements of rows indexed from 0 to 3, 3 not included
-and column indexed 2. Note that, the index before the colon is
-included and the index after it is not included in the slice that
-we have obtained. This is very similar to the ``range`` function,
-where ``range`` returns a list, in which the upper limit or stop
-value is not included.
-
-Now, if we wish to access the elements of row with index 2, and in
-columns indexed 0 to 2 (included), we say, 
-::
-
-  C[2, 0:3]
-
-Following is an exercise that you must do. 
-
-{{ show slide containing Question 3 }} 
-
-%%3%% First, obtain the elements [22, 23] from C. Then, obtain the
-elements [11, 21, 31, 41] from C. Finally, obtain the elements [21,
-31, 41, 0]. 
-
-Please, pause the video here. Do the exercises and then continue. 
-
-{{ show slide containing Solution 3 }}
-
-::
-
-  C[1, 1:3] 
-
-gives the elements [22, 23]
-::
-
-  C[0:4, 0]
-
-gives the elements [11, 21, 31, 41]
-::
-
-  C[1:5, 0]
-
-gives the elements [21, 31, 41, 0]
-
-Note that when specifying ranges, if you are starting from the
-beginning or going up-to the end, the corresponding element may be
-dropped. So, in the previous example to obtain [11, 21, 31, 41], we
-could have simply said, ::
-
-  C[:4, 0]
-
-and 
-::
-
-  C[1:, 0]
-
-gives the elements [21, 31, 41, 0]. If we skip both the indexes,
-we get the slice from end to end, as we already know. 
-
-Following is an exercise that you must do. 
-
-{{ show slide containing Question 4 }} 
-
-%%4%% Obtain the elements [[23, 24], [33, -34]] from C. 
-
-Please, pause the video here. Do the exercises and then continue. 
-
-{{ show slide containing Solution 4 }} 
-
-::
-
-  C[1:3, 2:4] 
-
-gives us the elements, [[23, 24], [33, -34]]. 
-
-Now, we wish to obtain the top left quarter of the image. How do
-we go about doing it? Since, we know the shape of the image to be
-300, we know that we need to get the first 150 rows and first 150
-columns. 
-::
-
-  I[:150, :150]
-
-gives us the top-left corner of the image. 
-
-We use the ``imshow`` command to see the slice we obtained in the
-form of an image and confirm. 
-::
-
-  imshow(I[:150, :150])
-
-Following is an exercise that you must do. 
-
-{{ show slide containing Question 5 }} 
-
-%%5%% Obtain the square in the center of the image.
-
-Please, pause the video here. Do the exercises and then continue. 
-
-{{ show slide containing Solution 5 }} 
-
-::
-
-  imshow(I[75:225, 75:225])
-
-Our next goal is to compress the image, using a very simple
-technique to reduce the space that the image takes on disk while
-not compromising too heavily on the image quality. The idea is to
-drop alternate rows and columns of the image and save it. This way
-we will be reducing the data to a fourth of the original data but
-losing only so much of visual information. 
-
-We shall first learn the idea of striding using the smaller array
-C. Suppose we wish to access only the odd rows and columns (first,
-third, fifth). We do this by, 
-::
-
-  C[0:5:2, 0:5:2]
-
-if we wish to be explicit, or simply, 
-::
-
-  C[::2, ::2]
-
-This is very similar to the step specified to the ``range``
-function. It specifies, the jump or step in which to move, while
-accessing the elements. If no step is specified, a default value
-of 1 is assumed. 
-::
-
-  C[1::2, ::2] 
-
-gives the elements, [[21, 23, 0], [41, 43, 0]]
-
-{{ show slide containing Question 6 }} 
-
-Following is an exercise that you must do. 
-
-%%6%% Obtain the following. 
-[[12, 0], [42, 0]]
-[[12, 13, 14], [0, 0, 0]]
-
-Please, pause the video here. Do the exercises and then continue. 
-
-{{ show slide containing Solution 6 }} 
-
-::
-
-  C[::3, 1::3]
-
-gives the elements [[12, 0], [42, 0]]
-::
-
-  C[::4, 1:4]
-
-gives the elements [[12, 13, 14], [0, 0, 0]]
-
-Now, that we know how to stride over an array, we can drop
-alternate rows and columns out of the image in I. 
-::
-
-  I[::2, ::2]
-
-To see this image, we say, 
-::
-
-  imshow(I[::2, ::2])
-
-This does not have much data to notice any real difference, but
-notice that the scale has reduced to show that we have dropped
-alternate rows and columns. If you notice carefully, you will be
-able to observe some blurring near the edges. To notice this
-effect more clearly, increase the step to 4. 
-::
-
-  imshow(I[::4, ::4])
-
-{{{ show summary slide }}}
-
-That brings us to the end of this tutorial. In this tutorial, we
-have learnt to access parts of arrays, specifically individual
-elements, rows and columns and larger pieces of arrays. We have
-also learnt how to modify arrays, element wise or in larger
-pieces.
-
-{{{ Show the "sponsored by FOSSEE" slide }}}
-
-This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India
-
-Hope you have enjoyed and found it useful.
-Thank you!
-
-.. 
-   Local Variables:
-   mode: rst
-   indent-tabs-mode: nil
-   sentence-end-double-space: nil
-   fill-column: 70
-   End:

--- a/accessing-pieces-arrays/slides.org	Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,123 +0,0 @@
-#+LaTeX_CLASS: beamer
-#+LaTeX_CLASS_OPTIONS: [presentation]
-#+BEAMER_FRAME_LEVEL: 1
-
-#+BEAMER_HEADER_EXTRA: \usetheme{Antibes}\usecolortheme{lily}\useoutertheme{infolines}\setbeamercovered{transparent}
-#+COLUMNS: %45ITEM %10BEAMER_env(Env) %10BEAMER_envargs(Env Args) %4BEAMER_col(Col) %8BEAMER_extra(Extra)
-#+PROPERTY: BEAMER_col_ALL 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 :ETC
-
-#+LaTeX_CLASS: beamer
-#+LaTeX_CLASS_OPTIONS: [presentation]
-
-#+LaTeX_HEADER: \usepackage[english]{babel} \usepackage{ae,aecompl}
-#+LaTeX_HEADER: \usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
-
-#+LaTeX_HEADER: \usepackage{listings}
-
-#+LaTeX_HEADER:\lstset{language=Python, basicstyle=\ttfamily\bfseries,
-#+LaTeX_HEADER:  commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
-#+LaTeX_HEADER:  showstringspaces=false, keywordstyle=\color{blue}\bfseries}
-
-#+TITLE:    Accessing parts of arrays
-#+AUTHOR:    FOSSEE
-#+EMAIL:     
-#+DATE:    
-
-#+DESCRIPTION: 
-#+KEYWORDS: 
-#+LANGUAGE:  en
-#+OPTIONS:   H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
-#+OPTIONS:   TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc
-
-* Outline
-  - Manipulating one and multi dimensional arrays
-  - Access and change individual elements 
-  - Access and change rows and columns 
-  - Slicing and striding on arrays to access chunks 
-  - Read images into arrays and manipulations
-* Sample Arrays
-  #+begin_src python
-    In []: A = array([12, 23, 34, 45, 56])
-    
-    In []: C = array([[11, 12, 13, 14, 15],
-                      [21, 22, 23, 24, 25],
-                      [31, 32, 33, 34, 35],
-                      [41, 42, 43, 44, 45],
-                      [51, 52, 53, 54, 55]])
-    
-  #+end_src
-* Question 1
-  Change the last column of ~C~ to zeroes. 
-* Solution 1
-  #+begin_src python
-    In []:  C[:, -1] = 0
-  #+end_src
-* Question 2
-  Change ~A~ to ~[11, 12, 13, 14, 15]~. 
-* Solution 2
-  #+begin_src python
-    In []:  A[:] = [11, 12, 13, 14, 15]
-  #+end_src
-* squares.png
-  #+begin_latex
-    \begin{center}
-      \includegraphics[scale=0.6]{squares}    
-    \end{center}
-  #+end_latex
-* Question 3
-  - obtain ~[22, 23]~ from ~C~. 
-  - obtain ~[11, 21, 31, 41]~ from ~C~. 
-  - obtain ~[21, 31, 41, 0]~.   
-* Solution 3
-  #+begin_src python
-    In []:  C[1, 1:3]
-    In []:  C[0:4, 0]
-    In []:  C[1:5, 0]
-  #+end_src
-* Question 4
-  Obtain ~[[23, 24], [33, -34]]~ from ~C~
-* Solution 4
-  #+begin_src python
-    In []:  C[1:3, 2:4]
-  #+end_src
-* Question 5
-  Obtain the square in the center of the image
-* Solution 5
-  #+begin_src python
-    In []: imshow(I[75:225, 75:225])
-  #+end_src
-* Question 6
-  Obtain the following
-  #+begin_src python
-    [[12, 0], [42, 0]]
-    [[12, 13, 14], [0, 0, 0]]
-  #+end_src
-
-* Solution 6
-  #+begin_src python
-    In []: C[::3, 1::3]
-    In []: C[::4, 1:4]
-  #+end_src
-* Summary
-  You should now be able to --
-  - Manipulate single \& multi dimensional arrays
-      - Access and change individual elements 
-      - Access and change rows and columns 
-      - Slice and stride on arrays
-  - Read images into arrays and manipulate them.
-* Thank you!
-#+begin_latex
-  \begin{block}{}
-  \begin{center}
-  This spoken tutorial has been produced by the
-  \textcolor{blue}{FOSSEE} team, which is funded by the 
-  \end{center}
-  \begin{center}
-    \textcolor{blue}{National Mission on Education through \\
-      Information \& Communication Technology \\ 
-      MHRD, Govt. of India}.
-  \end{center}  
-  \end{block}
-#+end_latex
-
-

--- a/accessing-pieces-arrays/slides.org.orig	Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,123 +0,0 @@
-#+LaTeX_CLASS: beamer
-#+LaTeX_CLASS_OPTIONS: [presentation]
-#+BEAMER_FRAME_LEVEL: 1
-
-#+BEAMER_HEADER_EXTRA: \usetheme{Antibes}\usecolortheme{lily}\useoutertheme{infolines}\setbeamercovered{transparent}
-#+COLUMNS: %45ITEM %10BEAMER_env(Env) %10BEAMER_envargs(Env Args) %4BEAMER_col(Col) %8BEAMER_extra(Extra)
-#+PROPERTY: BEAMER_col_ALL 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 :ETC
-
-#+LaTeX_CLASS: beamer
-#+LaTeX_CLASS_OPTIONS: [presentation]
-
-#+LaTeX_HEADER: \usepackage[english]{babel} \usepackage{ae,aecompl}
-#+LaTeX_HEADER: \usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
-
-#+LaTeX_HEADER: \usepackage{listings}
-
-#+LaTeX_HEADER:\lstset{language=Python, basicstyle=\ttfamily\bfseries,
-#+LaTeX_HEADER:  commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
-#+LaTeX_HEADER:  showstringspaces=false, keywordstyle=\color{blue}\bfseries}
-
-#+TITLE:    Accessing parts of arrays
-#+AUTHOR:    FOSSEE
-#+EMAIL:     
-#+DATE:    
-
-#+DESCRIPTION: 
-#+KEYWORDS: 
-#+LANGUAGE:  en
-#+OPTIONS:   H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
-#+OPTIONS:   TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc
-
-* Outline
-  - Manipulating one and multi dimensional arrays
-  - Access and change individual elements 
-  - Access and change rows and columns 
-  - Slicing and striding on arrays to access chunks 
-  - Read images into arrays and manipulations
-* Sample Arrays
-  #+begin_src python
-    In []: A = array([12, 23, 34, 45, 56])
-    
-    In []: C = array([[11, 12, 13, 14, 15],
-                      [21, 22, 23, 24, 25],
-                      [31, 32, 33, 34, 35],
-                      [41, 42, 43, 44, 45],
-                      [51, 52, 53, 54, 55]])
-    
-  #+end_src
-* Question 1
-  Change the last column of ~C~ to zeroes. 
-* Solution 1
-  #+begin_src python
-    In []:  C[:, -1] = 0
-  #+end_src
-* Question 2
-  Change ~A~ to ~[11, 12, 13, 14, 15]~. 
-* Solution 2
-  #+begin_src python
-    In []:  A[:] = [11, 12, 13, 14, 15]
-  #+end_src
-* squares.png
-  #+begin_latex
-    \begin{center}
-      \includegraphics[scale=0.6]{squares}    
-    \end{center}
-  #+end_latex
-* Question 3
-  - obtain ~[22, 23]~ from ~C~. 
-  - obtain ~[11, 21, 31, 41]~ from ~C~. 
-  - obtain ~[21, 31, 41, 0]~.   
-* Solution 3
-  #+begin_src python
-    In []:  C[1, 1:3]
-    In []:  C[0:4, 0]
-    In []:  C[1:5, 0]
-  #+end_src
-* Question 4
-  Obtain ~[[23, 24], [33, -34]]~ from ~C~
-* Solution 4
-  #+begin_src python
-    In []:  C[1:3, 2:4]
-  #+end_src
-* Question 5
-  Obtain the square in the center of the image
-* Solution 5
-  #+begin_src python
-    In []: imshow(I[75:225, 75:225])
-  #+end_src
-* Question 6
-  Obtain the following
-  #+begin_src python
-    [[12, 0], [42, 0]]
-    [[12, 13, 14], [0, 0, 0]]
-  #+end_src
-
-* Solution 6
-  #+begin_src python
-    In []: C[::3, 1::3]
-    In []: C[::4, 1:4]
-  #+end_src
-* Summary
-  You should now be able to --
-  - Manipulate single \& multi dimensional arrays
-      - Access and change individual elements 
-      - Access and change rows and columns 
-      - Slice and stride on arrays
-  - Read images into arrays and manipulate them.
-* Thank you!
-#+begin_latex
-  \begin{block}{}
-  \begin{center}
-  This spoken tutorial has been produced by the
-  \textcolor{blue}{FOSSEE} team, which is funded by the 
-  \end{center}
-  \begin{center}
-    \textcolor{blue}{National Mission on Education through \\
-      Information \& Communication Technology \\ 
-      MHRD, Govt. of India}.
-  \end{center}  
-  \end{block}
-#+end_latex
-
-

--- a/accessing-pieces-arrays/slides.tex	Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,214 +0,0 @@
-% Created 2010-11-02 Tue 17:47
-\documentclass[presentation]{beamer}
-\usepackage[latin1]{inputenc}
-\usepackage[T1]{fontenc}
-\usepackage{fixltx2e}
-\usepackage{graphicx}
-\usepackage{longtable}
-\usepackage{float}
-\usepackage{wrapfig}
-\usepackage{soul}
-\usepackage{textcomp}
-\usepackage{marvosym}
-\usepackage{wasysym}
-\usepackage{latexsym}
-\usepackage{amssymb}
-\usepackage{hyperref}
-\tolerance=1000
-\usepackage[english]{babel} \usepackage{ae,aecompl}
-\usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
-\usepackage{listings}
-\lstset{language=Python, basicstyle=\ttfamily\bfseries,
-commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
-showstringspaces=false, keywordstyle=\color{blue}\bfseries}
-\providecommand{\alert}[1]{\textbf{#1}}
-
-\title{Accessing parts of arrays}
-\author{FOSSEE}
-\date{}
-
-\usetheme{Antibes}\usecolortheme{lily}\useoutertheme{infolines}\setbeamercovered{transparent}
-\begin{document}
-
-\maketitle
-
-
-
-
-
-
-
-
-
-\begin{frame}
-\frametitle{Outline}
-\label{sec-1}
-
-\begin{itemize}
-\item Manipulating one and multi dimensional arrays
-\item Access and change individual elements
-\item Access and change rows and columns
-\item Slicing and striding on arrays to access chunks
-\item Read images into arrays and manipulations
-\end{itemize}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Sample Arrays}
-\label{sec-2}
-
-\lstset{language=Python}
-\begin{lstlisting}
-In []: A = array([12, 23, 34, 45, 56])
-
-In []: C = array([[11, 12, 13, 14, 15],
-                  [21, 22, 23, 24, 25],
-                  [31, 32, 33, 34, 35],
-                  [41, 42, 43, 44, 45],
-                  [51, 52, 53, 54, 55]])
-\end{lstlisting}
-\end{frame}
-\begin{frame}
-\frametitle{Question 1}
-\label{sec-3}
-
-  Change the last column of \texttt{C} to zeroes. 
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 1}
-\label{sec-4}
-
-\lstset{language=Python}
-\begin{lstlisting}
-In []:  C[:, -1] = 0
-\end{lstlisting}
-\end{frame}
-\begin{frame}
-\frametitle{Question 2}
-\label{sec-5}
-
-  Change \texttt{A} to \texttt{[11, 12, 13, 14, 15]}. 
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 2}
-\label{sec-6}
-
-\lstset{language=Python}
-\begin{lstlisting}
-In []:  A[:] = [11, 12, 13, 14, 15]
-\end{lstlisting}
-\end{frame}
-\begin{frame}
-\frametitle{squares.png}
-\label{sec-7}
-
-    \begin{center}
-      \includegraphics[scale=0.6]{squares}    
-    \end{center}
-\end{frame}
-\begin{frame}
-\frametitle{Question 3}
-\label{sec-8}
-
-\begin{itemize}
-\item obtain \texttt{[22, 23]} from \texttt{C}.
-\item obtain \texttt{[11, 21, 31, 41]} from \texttt{C}.
-\item obtain \texttt{[21, 31, 41, 0]}.
-\end{itemize}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 3}
-\label{sec-9}
-
-\lstset{language=Python}
-\begin{lstlisting}
-In []:  C[1, 1:3]
-In []:  C[0:4, 0]
-In []:  C[1:5, 0]
-\end{lstlisting}
-\end{frame}
-\begin{frame}
-\frametitle{Question 4}
-\label{sec-10}
-
-  Obtain \texttt{[[23, 24], [33, -34]]} from \texttt{C}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 4}
-\label{sec-11}
-
-\lstset{language=Python}
-\begin{lstlisting}
-In []:  C[1:3, 2:4]
-\end{lstlisting}
-\end{frame}
-\begin{frame}
-\frametitle{Question 5}
-\label{sec-12}
-
-  Obtain the square in the center of the image
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 5}
-\label{sec-13}
-
-\lstset{language=Python}
-\begin{lstlisting}
-In []: imshow(I[75:225, 75:225])
-\end{lstlisting}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Question 6}
-\label{sec-14}
-
-  Obtain the following
-\lstset{language=Python}
-\begin{lstlisting}
-[[12, 0], [42, 0]]
-[[12, 13, 14], [0, 0, 0]]
-\end{lstlisting}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 6}
-\label{sec-15}
-
-\lstset{language=Python}
-\begin{lstlisting}
-In []: C[::3, 1::3]
-In []: C[::4, 1:4]
-\end{lstlisting}
-\end{frame}
-\begin{frame}
-\frametitle{Summary}
-\label{sec-16}
-
-  You should now be able to --
-\begin{itemize}
-\item Manipulate single \& multi dimensional arrays
-
-\begin{itemize}
-\item Access and change individual elements
-\item Access and change rows and columns
-\item Slice and stride on arrays
-\end{itemize}
-
-\item Read images into arrays and manipulate them.
-\end{itemize}
-\end{frame}
-\begin{frame}
-\frametitle{Thank you!}
-\label{sec-17}
-
-  \begin{block}{}
-  \begin{center}
-  This spoken tutorial has been produced by the
-  \textcolor{blue}{FOSSEE} team, which is funded by the 
-  \end{center}
-  \begin{center}
-    \textcolor{blue}{National Mission on Education through \\
-      Information \& Communication Technology \\ 
-      MHRD, Govt. of India}.
-  \end{center}  
-  \end{block}
-\end{frame}
-
-\end{document}

--- a/accessing-pieces-arrays/slides.tex.orig	Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,199 +0,0 @@
-% Created 2010-11-03 Wed 15:37
-\documentclass[presentation]{beamer}
-\usetheme{Antibes}\usecolortheme{lily}\useoutertheme{infolines}\setbeamercovered{transparent}
-\usepackage[latin1]{inputenc}
-\usepackage[T1]{fontenc}
-\usepackage{graphicx}
-\usepackage{longtable}
-\usepackage{float}
-\usepackage{wrapfig}
-\usepackage{soul}
-\usepackage{amssymb}
-\usepackage{hyperref}
-\usepackage[english]{babel} \usepackage{ae,aecompl}
-\usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
-\usepackage{listings}
-\lstset{language=Python, basicstyle=\ttfamily\bfseries,
-commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
-showstringspaces=false, keywordstyle=\color{blue}\bfseries}
-
-\title{Accessing parts of arrays}
-\author{FOSSEE}
-\date{}
-
-\begin{document}
-
-\maketitle
-
-
-
-
-
-
-
-
-
-\begin{frame}
-\frametitle{Outline}
-\label{sec-1}
-
-\begin{itemize}
-\item Manipulating one and multi dimensional arrays
-\item Access and change individual elements
-\item Access and change rows and columns
-\item Slicing and striding on arrays to access chunks
-\item Read images into arrays and manipulations
-\end{itemize}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Sample Arrays}
-\label{sec-2}
-
-\begin{verbatim}
-In []: A = array([12, 23, 34, 45, 56])
-
-In []: C = array([[11, 12, 13, 14, 15],
-                  [21, 22, 23, 24, 25],
-                  [31, 32, 33, 34, 35],
-                  [41, 42, 43, 44, 45],
-                  [51, 52, 53, 54, 55]])
-\end{verbatim}
-\end{frame}
-\begin{frame}
-\frametitle{Question 1}
-\label{sec-3}
-
-  Change the last column of \texttt{C} to zeroes. 
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 1}
-\label{sec-4}
-
-\begin{verbatim}
-In []:  C[:, -1] = 0
-\end{verbatim}
-\end{frame}
-\begin{frame}
-\frametitle{Question 2}
-\label{sec-5}
-
-  Change \texttt{A} to \texttt{[11, 12, 13, 14, 15]}. 
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 2}
-\label{sec-6}
-
-\begin{verbatim}
-In []:  A[:] = [11, 12, 13, 14, 15]
-\end{verbatim}
-\end{frame}
-\begin{frame}
-\frametitle{squares.png}
-\label{sec-7}
-
-    \begin{center}
-      \includegraphics[scale=0.6]{squares}    
-    \end{center}
-\end{frame}
-\begin{frame}
-\frametitle{Question 3}
-\label{sec-8}
-
-\begin{itemize}
-\item obtain \texttt{[22, 23]} from \texttt{C}.
-\item obtain \texttt{[11, 21, 31, 41]} from \texttt{C}.
-\item obtain \texttt{[21, 31, 41, 0]}.
-\end{itemize}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 3}
-\label{sec-9}
-
-\begin{verbatim}
-In []:  C[1, 1:3]
-In []:  C[0:4, 0]
-In []:  C[1:5, 0]
-\end{verbatim}
-\end{frame}
-\begin{frame}
-\frametitle{Question 4}
-\label{sec-10}
-
-  Obtain \texttt{[[23, 24], [33, -34]]} from \texttt{C}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 4}
-\label{sec-11}
-
-\begin{verbatim}
-In []:  C[1:3, 2:4]
-\end{verbatim}
-\end{frame}
-\begin{frame}
-\frametitle{Question 5}
-\label{sec-12}
-
-  Obtain the square in the center of the image
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 5}
-\label{sec-13}
-
-\begin{verbatim}
-In []: imshow(I[75:225, 75:225])
-\end{verbatim}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Question 6}
-\label{sec-14}
-
-  Obtain the following
-\begin{verbatim}
-[[12, 0], [42, 0]]
-[[12, 13, 14], [0, 0, 0]]
-\end{verbatim}
-\end{frame}
-\begin{frame}[fragile]
-\frametitle{Solution 6}
-\label{sec-15}
-
-\begin{verbatim}
-In []: C[::3, 1::3]
-In []: C[::4, 1:4]
-\end{verbatim}
-\end{frame}
-\begin{frame}
-\frametitle{Summary}
-\label{sec-16}
-
-  You should now be able to --
-\begin{itemize}
-\item Manipulate single \& multi dimensional arrays
-
-\begin{itemize}
-\item Access and change individual elements
-\item Access and change rows and columns
-\item Slice and stride on arrays
-\end{itemize}
-
-\item Read images into arrays and manipulate them.
-\end{itemize}
-\end{frame}
-\begin{frame}
-\frametitle{Thank you!}
-\label{sec-17}
-
-  \begin{block}{}
-  \begin{center}
-  This spoken tutorial has been produced by the
-  \textcolor{blue}{FOSSEE} team, which is funded by the 
-  \end{center}
-  \begin{center}
-    \textcolor{blue}{National Mission on Education through \\
-      Information \& Communication Technology \\ 
-      MHRD, Govt. of India}.
-  \end{center}  
-  \end{block}
-\end{frame}
-
-\end{document}

Binary file accessing-pieces-arrays/squares.png has changed

Binary file accessing-pieces-arrays/tagore-einstein.png has changed

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessing_parts_of_arrays/questions.rst	Wed Dec 01 16:51:35 2010 +0530
@@ -0,0 +1,159 @@
+Objective Questions
+-------------------
+
+.. A mininum of 8 questions here (along with answers)
+
+1. Given the array, ``A = array([12, 15, 18, 21])``, how do we access
+   the element ``18``?
+
+   Answer: ``A[2]``
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, what element is
+   accessed by ``A[1]``
+
+   Answer: ``15``  
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, what element is
+   accessed by ``A[-3]``?
+
+   Answer: ``15``  
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, how do you change
+   the element ``15`` to ``51``?
+
+   Answer: ``A[1] = 51``
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, what is ``A``
+   after the execution of the statement ``A[3] = 24``?
+
+   Answer: ``array([12, 15, 18, 24])``
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, what is the
+   result of the statement, ``A[4] = 24``?
+
+   Answer: IndexError: index out of bounds
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, how do we
+   access the element ``18``? 
+
+   Answer: ``A[0, 0]``
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
+   result of ``B[1]``? 
+
+   Answer:  ``array([18, 21])``
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
+   result of ``B[1, 1]``?
+
+   Answer:  ``21``
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, what element
+   is accessed by ``B[-1, -2]``?
+
+   Answer:  ``18``   
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, how do you
+   change the element ``15`` to ``51``?
+
+   Answer:  ``B[0, 1] = 51``   
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
+   value of B, after executing, ``B[0] = 0``?
+
+   Answer:  ``array([[0, 0], [18, 21]])``   
+
+#. Given the array, 
+   
+   ::
+   
+     B = array([[10, 11, 12, 13],
+                [20, 21, 22, 23],
+                [30, 31, 32, 33],
+                [40, 41, 42, 43]])
+
+   Obtain the elements, ``[[21, 22], [32, 32]]``
+
+   Answer:  ``B[1:3, 1:3]``   
+
+#. Given the array, 
+   
+   ::
+   
+     B = array([[10, 11, 12, 13],
+                [20, 21, 22, 23],
+                [30, 31, 32, 33],
+                [40, 41, 42, 43]])
+
+   Obtain the elements, ``[[10, 13], [30, 33]]``
+
+   Answer:  ``B[::2, ::3]``
+
+#. What command is used to read an image file?
+
+   a. imshow
+   #. imread
+   #. imopen
+   #. open
+
+   Answer: ``imread``   
+
+#. If ``P`` is ``array([12, 13, 14, 15])`` then ``P.shape`` gives
+   ``(4, 1)``. True or False?
+
+   Answer: False
+     
+Larger Questions
+----------------
+
+.. A minimum of 2 questions here (along with answers)
+
+1. Given the array, 
+   ::
+   
+     B = array([[10, 11, 12, 13],
+                [20, 21, 22, 23],
+                [30, 31, 32, 33],
+                [40, 41, 42, 43]])
+
+   Change the array to 
+   ::
+   
+     B = array([[10, 11, 10, 11],
+                [20, 21, 20, 21],
+                [10, 11, 10, 11],
+                [20, 21, 20, 21]])
+
+   using slicing and striding. 
+
+   Answer::
+
+     B[:2, 2:] = B[:2, :2]
+     B[2:, :2] = B[:2, :2]
+     B[2:, 2:] = B[:2, :2]
+
+#. Find out how to display a grayscale image with proper colors. Hint,
+   use ``?`` on ``imshow``. 
+   
+   Answer: ``cmap=cm.gray``
+                  
+#. From the image, ``tagore-einstein.png``, 
+   a. show only the face of Einstein. 
+   b. show only the face of Tagore. 
+
+   Hint, use ``imread`` to read the image and ``imshow`` to show the
+   image.  Use ``cm.gray`` as ``cmap`` to display the image properly.   
+
+   Answer:: 
+
+     F = imread('tagore-einstein.png')
+     imshow(F[:210, 20:180], cmap=cm.gray)
+
+     F = imread('tagore-einstein.png')
+     imshow(F[30:300, 320:480], cmap=cm.gray)
+
+.. #[Puneeth: This question contains answer to previous
+.. question. Shouldn't be shown at the same time.]
+
+
+          

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessing_parts_of_arrays/quickref.tex	Wed Dec 01 16:51:35 2010 +0530
@@ -0,0 +1,12 @@
+\textbf{Accessing parts of arrays}
+
+\lstinline|C[i-1, j-1]| to access element i, j in C (mxn).
+\lstinline|C[i-1]| to access i^{th} row
+\lstinline|C[:, j-1]| to access j^{th} column
+
+Assigning to accessed elements, changes them. 
+
+\lstinline|A[m:n:o]| accesses the rows from \lstinline|m|
+to \lstinline|n| (excluded) in steps of \lstinline|o|
+
+Similarly, \lstinline|C[m:n:o, p:q:r]|

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessing_parts_of_arrays/script.rst	Wed Dec 01 16:51:35 2010 +0530
@@ -0,0 +1,426 @@
+.. Objectives
+.. ----------
+   
+   .. By the end of this tutorial, you will be able to:
+   
+   ..   1. Access and change individual elements of arrays, both one
+   ..   dimensional and multi-dimensional.
+   ..   2. Access and change rows and columns of arrays. 
+   ..   3. Access and change other chunks from an array, using slicing
+   ..   and striding. 
+   ..   4. Read images into arrays and perform processing on them, using
+   ..   simple array manipulations. 
+
+.. Prerequisites
+.. -------------
+
+..   1. getting started with arrays
+
+.. #[anand: internal reviewer not mentioned]     
+.. Author              : Puneeth
+   Internal Reviewer   : 
+   External Reviewer   :
+   Language Reviewer   : Bhanukiran
+   Checklist OK?       : <06-11-2010, Anand,  OK> [2010-10-05]
+
+Script
+------
+
+{{{ Screen shows welcome slide }}}
+
+Welcome to the tutorial on accessing pieces of arrays
+
+{{{ Show the outline for this tutorial }}} 
+
+In this tutorial we shall learn to access individual elements of
+arrays, get rows and columns and other chunks of arrays using
+slicing and striding. 
+
+{{{ switch back to the terminal }}}
+
+As usual, we start IPython, using 
+::
+
+  ipython -pylab 
+
+
+{{ Show the slide with the arrays, A and C }}
+
+Let us have two arrays, A and C, as the sample arrays that we will
+use to work through this tutorial. 
+
+::
+
+  A = array([12, 23, 34, 45, 56])
+
+  C = array([[11, 12, 13, 14, 15],
+             [21, 22, 23, 24, 25],
+             [31, 32, 33, 34, 35],
+             [41, 42, 43, 44, 45],
+             [51, 52, 53, 54, 55]])
+
+Pause the video here and make sure you have the arrays A and C,
+typed in correctly.
+
+{{{ Pause the recording and type the arrays A,C }}}
+
+Let us begin with the most elementary thing, accessing individual
+elements. Also, let us first do it with the one-dimensional array
+A, and then do the same thing with the two-dimensional array. 
+
+To access, the element 34 in A, we say, 
+
+::
+
+  A[2]
+
+A of 2, note that we are using square brackets.
+
+Like lists, indexing starts from 0 in arrays, too. So, 34, the
+third element has the index 2. 
+
+Now, let us access the element 34 from C. To do this, we say
+::
+
+  C[2, 3]
+
+C of 2,3.
+
+34 is in the third row and the fourth column, and since indexing
+begins from zero, the row index is 2 and column index is 3. 
+
+Now, that we have accessed one element of the array, let us change
+it. We shall change the 34 to -34 in both A and C. To do this, we
+simply assign the new value after accessing the element. 
+::
+
+  A[2] = -34
+  C[2, 3] = -34
+
+Now that we have accessed and changed a single element, let us
+access and change more than one element at a time; first rows and
+then columns.
+
+Let us access one row of C, say the third row. We do it by saying, 
+::
+
+  C[2] 
+
+How do we access the last row of C? We could say,
+::
+
+  C[4] 
+
+for the fifth row, or as with lists, use negative indexing and say
+::
+
+  C[-1]
+
+Now, we could change the last row into all zeros, using either 
+::
+
+  C[-1] = [0, 0, 0, 0, 0]
+
+or 
+
+::
+  
+  C[-1] = 0
+
+Now, how do we access one column of C? As with accessing individual
+elements, the column is the second parameter to be specified (after
+the comma). The first parameter, is replaced with a ``:``. This
+specifies that we want all the elements of that dimension, instead of
+just one particular element. We access the third column by
+
+::
+  
+  C[:, 2]
+
+Following is an exercise that you must do. 
+
+{{ show slide containing Question 1}} 
+
+%%1%% Change the last column of C to zeroes. 
+
+Please, pause the video here. Do the exercises and then continue. 
+
+::
+  
+  C[:, -1] = 0
+
+Since A is one dimensional, rows and columns of A don't make much
+sense. It has just one row and 
+::
+
+  A[:] 
+
+gives the whole of A. 
+
+Following is an exercise that you must do. 
+
+{{ show slide containing Question 2}} 
+
+%%2%% Change ``A`` to ``[11, 12, 13, 14, 15]``. 
+
+Please, pause the video here. Do the exercises and then continue. 
+
+To change A, we say
+::
+
+  A[:] = [11, 12, 13, 14, 15]
+
+Now, that we know how to access, rows and columns of an array, we
+shall learn how to access other pieces of an array. For this
+purpose, we will be using image arrays. 
+
+To read an image into an array, we use the ``imread`` command. We
+shall use the image ``squares.png`` present in ``/home/fossee``. We
+shall first navigate to that path in the OS and see what the image
+contains. 
+
+{{{ switch to the browser and show the image }}}
+
+{{{ switch back to the ipython terminal }}}
+
+Let us now read the data in ``squares.png`` into the array ``I``. 
+::
+
+  I = imread('/home/fossee/squares.png')
+
+We can see the contents of the image, using the command
+``imshow``. We say, 
+::
+
+  imshow(I) 
+
+to see what has been read into ``I``. We do not see white and black
+because, ``pylab`` has mapped white and black to different
+colors. This can be changed by using a different colormap. 
+
+To see that ``I`` is really, just an array, we say, 
+::
+
+  I 
+
+at the prompt, and see that an array is displayed. 
+
+To check the dimensions of any array, we can use ``.shape``. We say
+
+::
+
+  I.shape 
+
+to get the dimensions of the image. As we can see, ``squares.png``
+has the dimensions of 300x300. 
+
+Our goal for this part of the tutorial would be to get the
+top-left quadrant of the image. To do this, we need to access, a
+few of the rows and a few of the columns of the array. 
+
+To access, the third column of C, we said, ``C[:, 2]``. Essentially,
+we are accessing all the rows in column three of C. Now, let us
+modify this to access only the first three rows, of column three
+of C. 
+
+We say, 
+::
+
+  C[0:3, 2]
+
+to get the elements of rows indexed from 0 to 3, 3 not included
+and column indexed 2. Note that, the index before the colon is
+included and the index after it is not included in the slice that
+we have obtained. This is very similar to the ``range`` function,
+where ``range`` returns a list, in which the upper limit or stop
+value is not included.
+
+Now, if we wish to access the elements of row with index 2, and in
+columns indexed 0 to 2 (included), we say, 
+::
+
+  C[2, 0:3]
+
+Following is an exercise that you must do. 
+
+{{ show slide containing Question 3 }} 
+
+%%3%% First, obtain the elements [22, 23] from C. Then, obtain the
+elements [11, 21, 31, 41] from C. Finally, obtain the elements [21,
+31, 41, 0]. 
+
+Please, pause the video here. Do the exercises and then continue. 
+
+{{ show slide containing Solution 3 }}
+
+::
+
+  C[1, 1:3] 
+
+gives the elements [22, 23]
+::
+
+  C[0:4, 0]
+
+gives the elements [11, 21, 31, 41]
+::
+
+  C[1:5, 0]
+
+gives the elements [21, 31, 41, 0]
+
+Note that when specifying ranges, if you are starting from the
+beginning or going up-to the end, the corresponding element may be
+dropped. So, in the previous example to obtain [11, 21, 31, 41], we
+could have simply said, ::
+
+  C[:4, 0]
+
+and 
+::
+
+  C[1:, 0]
+
+gives the elements [21, 31, 41, 0]. If we skip both the indexes,
+we get the slice from end to end, as we already know. 
+
+Following is an exercise that you must do. 
+
+{{ show slide containing Question 4 }} 
+
+%%4%% Obtain the elements [[23, 24], [33, -34]] from C. 
+
+Please, pause the video here. Do the exercises and then continue. 
+
+{{ show slide containing Solution 4 }} 
+
+::
+
+  C[1:3, 2:4] 
+
+gives us the elements, [[23, 24], [33, -34]]. 
+
+Now, we wish to obtain the top left quarter of the image. How do
+we go about doing it? Since, we know the shape of the image to be
+300, we know that we need to get the first 150 rows and first 150
+columns. 
+::
+
+  I[:150, :150]
+
+gives us the top-left corner of the image. 
+
+We use the ``imshow`` command to see the slice we obtained in the
+form of an image and confirm. 
+::
+
+  imshow(I[:150, :150])
+
+Following is an exercise that you must do. 
+
+{{ show slide containing Question 5 }} 
+
+%%5%% Obtain the square in the center of the image.
+
+Please, pause the video here. Do the exercises and then continue. 
+
+{{ show slide containing Solution 5 }} 
+
+::
+
+  imshow(I[75:225, 75:225])
+
+Our next goal is to compress the image, using a very simple
+technique to reduce the space that the image takes on disk while
+not compromising too heavily on the image quality. The idea is to
+drop alternate rows and columns of the image and save it. This way
+we will be reducing the data to a fourth of the original data but
+losing only so much of visual information. 
+
+We shall first learn the idea of striding using the smaller array
+C. Suppose we wish to access only the odd rows and columns (first,
+third, fifth). We do this by, 
+::
+
+  C[0:5:2, 0:5:2]
+
+if we wish to be explicit, or simply, 
+::
+
+  C[::2, ::2]
+
+This is very similar to the step specified to the ``range``
+function. It specifies, the jump or step in which to move, while
+accessing the elements. If no step is specified, a default value
+of 1 is assumed. 
+::
+
+  C[1::2, ::2] 
+
+gives the elements, [[21, 23, 0], [41, 43, 0]]
+
+{{ show slide containing Question 6 }} 
+
+Following is an exercise that you must do. 
+
+%%6%% Obtain the following. 
+[[12, 0], [42, 0]]
+[[12, 13, 14], [0, 0, 0]]
+
+Please, pause the video here. Do the exercises and then continue. 
+
+{{ show slide containing Solution 6 }} 
+
+::
+
+  C[::3, 1::3]
+
+gives the elements [[12, 0], [42, 0]]
+::
+
+  C[::4, 1:4]
+
+gives the elements [[12, 13, 14], [0, 0, 0]]
+
+Now, that we know how to stride over an array, we can drop
+alternate rows and columns out of the image in I. 
+::
+
+  I[::2, ::2]
+
+To see this image, we say, 
+::
+
+  imshow(I[::2, ::2])
+
+This does not have much data to notice any real difference, but
+notice that the scale has reduced to show that we have dropped
+alternate rows and columns. If you notice carefully, you will be
+able to observe some blurring near the edges. To notice this
+effect more clearly, increase the step to 4. 
+::
+
+  imshow(I[::4, ::4])
+
+{{{ show summary slide }}}
+
+That brings us to the end of this tutorial. In this tutorial, we
+have learnt to access parts of arrays, specifically individual
+elements, rows and columns and larger pieces of arrays. We have
+also learnt how to modify arrays, element wise or in larger
+pieces.
+
+{{{ Show the "sponsored by FOSSEE" slide }}}
+
+This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India
+
+Hope you have enjoyed and found it useful.
+Thank you!
+
+.. 
+   Local Variables:
+   mode: rst
+   indent-tabs-mode: nil
+   sentence-end-double-space: nil
+   fill-column: 70
+   End:

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessing_parts_of_arrays/slides.org	Wed Dec 01 16:51:35 2010 +0530
@@ -0,0 +1,123 @@
+#+LaTeX_CLASS: beamer
+#+LaTeX_CLASS_OPTIONS: [presentation]
+#+BEAMER_FRAME_LEVEL: 1
+
+#+BEAMER_HEADER_EXTRA: \usetheme{Antibes}\usecolortheme{lily}\useoutertheme{infolines}\setbeamercovered{transparent}
+#+COLUMNS: %45ITEM %10BEAMER_env(Env) %10BEAMER_envargs(Env Args) %4BEAMER_col(Col) %8BEAMER_extra(Extra)
+#+PROPERTY: BEAMER_col_ALL 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 :ETC
+
+#+LaTeX_CLASS: beamer
+#+LaTeX_CLASS_OPTIONS: [presentation]
+
+#+LaTeX_HEADER: \usepackage[english]{babel} \usepackage{ae,aecompl}
+#+LaTeX_HEADER: \usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
+
+#+LaTeX_HEADER: \usepackage{listings}
+
+#+LaTeX_HEADER:\lstset{language=Python, basicstyle=\ttfamily\bfseries,
+#+LaTeX_HEADER:  commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
+#+LaTeX_HEADER:  showstringspaces=false, keywordstyle=\color{blue}\bfseries}
+
+#+TITLE:    Accessing parts of arrays
+#+AUTHOR:    FOSSEE
+#+EMAIL:     
+#+DATE:    
+
+#+DESCRIPTION: 
+#+KEYWORDS: 
+#+LANGUAGE:  en
+#+OPTIONS:   H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
+#+OPTIONS:   TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc
+
+* Outline
+  - Manipulating one and multi dimensional arrays
+  - Access and change individual elements 
+  - Access and change rows and columns 
+  - Slicing and striding on arrays to access chunks 
+  - Read images into arrays and manipulations
+* Sample Arrays
+  #+begin_src python
+    In []: A = array([12, 23, 34, 45, 56])
+    
+    In []: C = array([[11, 12, 13, 14, 15],
+                      [21, 22, 23, 24, 25],
+                      [31, 32, 33, 34, 35],
+                      [41, 42, 43, 44, 45],
+                      [51, 52, 53, 54, 55]])
+    
+  #+end_src
+* Question 1
+  Change the last column of ~C~ to zeroes. 
+* Solution 1
+  #+begin_src python
+    In []:  C[:, -1] = 0
+  #+end_src
+* Question 2
+  Change ~A~ to ~[11, 12, 13, 14, 15]~. 
+* Solution 2
+  #+begin_src python
+    In []:  A[:] = [11, 12, 13, 14, 15]
+  #+end_src
+* squares.png
+  #+begin_latex
+    \begin{center}
+      \includegraphics[scale=0.6]{squares}    
+    \end{center}
+  #+end_latex
+* Question 3
+  - obtain ~[22, 23]~ from ~C~. 
+  - obtain ~[11, 21, 31, 41]~ from ~C~. 
+  - obtain ~[21, 31, 41, 0]~.   
+* Solution 3
+  #+begin_src python
+    In []:  C[1, 1:3]
+    In []:  C[0:4, 0]
+    In []:  C[1:5, 0]
+  #+end_src
+* Question 4
+  Obtain ~[[23, 24], [33, -34]]~ from ~C~
+* Solution 4
+  #+begin_src python
+    In []:  C[1:3, 2:4]
+  #+end_src
+* Question 5
+  Obtain the square in the center of the image
+* Solution 5
+  #+begin_src python
+    In []: imshow(I[75:225, 75:225])
+  #+end_src
+* Question 6
+  Obtain the following
+  #+begin_src python
+    [[12, 0], [42, 0]]
+    [[12, 13, 14], [0, 0, 0]]
+  #+end_src
+
+* Solution 6
+  #+begin_src python
+    In []: C[::3, 1::3]
+    In []: C[::4, 1:4]
+  #+end_src
+* Summary
+  You should now be able to --
+  - Manipulate single \& multi dimensional arrays
+      - Access and change individual elements 
+      - Access and change rows and columns 
+      - Slice and stride on arrays
+  - Read images into arrays and manipulate them.
+* Thank you!
+#+begin_latex
+  \begin{block}{}
+  \begin{center}
+  This spoken tutorial has been produced by the
+  \textcolor{blue}{FOSSEE} team, which is funded by the 
+  \end{center}
+  \begin{center}
+    \textcolor{blue}{National Mission on Education through \\
+      Information \& Communication Technology \\ 
+      MHRD, Govt. of India}.
+  \end{center}  
+  \end{block}
+#+end_latex
+
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessing_parts_of_arrays/slides.org.orig	Wed Dec 01 16:51:35 2010 +0530
@@ -0,0 +1,123 @@
+#+LaTeX_CLASS: beamer
+#+LaTeX_CLASS_OPTIONS: [presentation]
+#+BEAMER_FRAME_LEVEL: 1
+
+#+BEAMER_HEADER_EXTRA: \usetheme{Antibes}\usecolortheme{lily}\useoutertheme{infolines}\setbeamercovered{transparent}
+#+COLUMNS: %45ITEM %10BEAMER_env(Env) %10BEAMER_envargs(Env Args) %4BEAMER_col(Col) %8BEAMER_extra(Extra)
+#+PROPERTY: BEAMER_col_ALL 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 :ETC
+
+#+LaTeX_CLASS: beamer
+#+LaTeX_CLASS_OPTIONS: [presentation]
+
+#+LaTeX_HEADER: \usepackage[english]{babel} \usepackage{ae,aecompl}
+#+LaTeX_HEADER: \usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
+
+#+LaTeX_HEADER: \usepackage{listings}
+
+#+LaTeX_HEADER:\lstset{language=Python, basicstyle=\ttfamily\bfseries,
+#+LaTeX_HEADER:  commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
+#+LaTeX_HEADER:  showstringspaces=false, keywordstyle=\color{blue}\bfseries}
+
+#+TITLE:    Accessing parts of arrays
+#+AUTHOR:    FOSSEE
+#+EMAIL:     
+#+DATE:    
+
+#+DESCRIPTION: 
+#+KEYWORDS: 
+#+LANGUAGE:  en
+#+OPTIONS:   H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
+#+OPTIONS:   TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc
+
+* Outline
+  - Manipulating one and multi dimensional arrays
+  - Access and change individual elements 
+  - Access and change rows and columns 
+  - Slicing and striding on arrays to access chunks 
+  - Read images into arrays and manipulations
+* Sample Arrays
+  #+begin_src python
+    In []: A = array([12, 23, 34, 45, 56])
+    
+    In []: C = array([[11, 12, 13, 14, 15],
+                      [21, 22, 23, 24, 25],
+                      [31, 32, 33, 34, 35],
+                      [41, 42, 43, 44, 45],
+                      [51, 52, 53, 54, 55]])
+    
+  #+end_src
+* Question 1
+  Change the last column of ~C~ to zeroes. 
+* Solution 1
+  #+begin_src python
+    In []:  C[:, -1] = 0
+  #+end_src
+* Question 2
+  Change ~A~ to ~[11, 12, 13, 14, 15]~. 
+* Solution 2
+  #+begin_src python
+    In []:  A[:] = [11, 12, 13, 14, 15]
+  #+end_src
+* squares.png
+  #+begin_latex
+    \begin{center}
+      \includegraphics[scale=0.6]{squares}    
+    \end{center}
+  #+end_latex
+* Question 3
+  - obtain ~[22, 23]~ from ~C~. 
+  - obtain ~[11, 21, 31, 41]~ from ~C~. 
+  - obtain ~[21, 31, 41, 0]~.   
+* Solution 3
+  #+begin_src python
+    In []:  C[1, 1:3]
+    In []:  C[0:4, 0]
+    In []:  C[1:5, 0]
+  #+end_src
+* Question 4
+  Obtain ~[[23, 24], [33, -34]]~ from ~C~
+* Solution 4
+  #+begin_src python
+    In []:  C[1:3, 2:4]
+  #+end_src
+* Question 5
+  Obtain the square in the center of the image
+* Solution 5
+  #+begin_src python
+    In []: imshow(I[75:225, 75:225])
+  #+end_src
+* Question 6
+  Obtain the following
+  #+begin_src python
+    [[12, 0], [42, 0]]
+    [[12, 13, 14], [0, 0, 0]]
+  #+end_src
+
+* Solution 6
+  #+begin_src python
+    In []: C[::3, 1::3]
+    In []: C[::4, 1:4]
+  #+end_src
+* Summary
+  You should now be able to --
+  - Manipulate single \& multi dimensional arrays
+      - Access and change individual elements 
+      - Access and change rows and columns 
+      - Slice and stride on arrays
+  - Read images into arrays and manipulate them.
+* Thank you!
+#+begin_latex
+  \begin{block}{}
+  \begin{center}
+  This spoken tutorial has been produced by the
+  \textcolor{blue}{FOSSEE} team, which is funded by the 
+  \end{center}
+  \begin{center}
+    \textcolor{blue}{National Mission on Education through \\
+      Information \& Communication Technology \\ 
+      MHRD, Govt. of India}.
+  \end{center}  
+  \end{block}
+#+end_latex
+
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessing_parts_of_arrays/slides.tex	Wed Dec 01 16:51:35 2010 +0530
@@ -0,0 +1,214 @@
+% Created 2010-11-02 Tue 17:47
+\documentclass[presentation]{beamer}
+\usepackage[latin1]{inputenc}
+\usepackage[T1]{fontenc}
+\usepackage{fixltx2e}
+\usepackage{graphicx}
+\usepackage{longtable}
+\usepackage{float}
+\usepackage{wrapfig}
+\usepackage{soul}
+\usepackage{textcomp}
+\usepackage{marvosym}
+\usepackage{wasysym}
+\usepackage{latexsym}
+\usepackage{amssymb}
+\usepackage{hyperref}
+\tolerance=1000
+\usepackage[english]{babel} \usepackage{ae,aecompl}
+\usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
+\usepackage{listings}
+\lstset{language=Python, basicstyle=\ttfamily\bfseries,
+commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
+showstringspaces=false, keywordstyle=\color{blue}\bfseries}
+\providecommand{\alert}[1]{\textbf{#1}}
+
+\title{Accessing parts of arrays}
+\author{FOSSEE}
+\date{}
+
+\usetheme{Antibes}\usecolortheme{lily}\useoutertheme{infolines}\setbeamercovered{transparent}
+\begin{document}
+
+\maketitle
+
+
+
+
+
+
+
+
+
+\begin{frame}
+\frametitle{Outline}
+\label{sec-1}
+
+\begin{itemize}
+\item Manipulating one and multi dimensional arrays
+\item Access and change individual elements
+\item Access and change rows and columns
+\item Slicing and striding on arrays to access chunks
+\item Read images into arrays and manipulations
+\end{itemize}
+\end{frame}
+\begin{frame}[fragile]
+\frametitle{Sample Arrays}
+\label{sec-2}
+
+\lstset{language=Python}
+\begin{lstlisting}
+In []: A = array([12, 23, 34, 45, 56])
+
+In []: C = array([[11, 12, 13, 14, 15],
+                  [21, 22, 23, 24, 25],
+                  [31, 32, 33, 34, 35],
+                  [41, 42, 43, 44, 45],
+                  [51, 52, 53, 54, 55]])
+\end{lstlisting}
+\end{frame}
+\begin{frame}
+\frametitle{Question 1}
+\label{sec-3}
+
+  Change the last column of \texttt{C} to zeroes. 
+\end{frame}
+\begin{frame}[fragile]
+\frametitle{Solution 1}
+\label{sec-4}
+
+\lstset{language=Python}
+\begin{lstlisting}
+In []:  C[:, -1] = 0
+\end{lstlisting}
+\end{frame}
+\begin{frame}
+\frametitle{Question 2}
+\label{sec-5}
+
+  Change \texttt{A} to \texttt{[11, 12, 13, 14, 15]}. 
+\end{frame}
+\begin{frame}[fragile]
+\frametitle{Solution 2}
+\label{sec-6}
+
+\lstset{language=Python}
+\begin{lstlisting}
+In []:  A[:] = [11, 12, 13, 14, 15]
+\end{lstlisting}
+\end{frame}
+\begin{frame}
+\frametitle{squares.png}
+\label{sec-7}
+
+    \begin{center}
+      \includegraphics[scale=0.6]{squares}    
+    \end{center}
+\end{frame}
+\begin{frame}
+\frametitle{Question 3}
+\label{sec-8}
+
+\begin{itemize}
+\item obtain \texttt{[22, 23]} from \texttt{C}.
+\item obtain \texttt{[11, 21, 31, 41]} from \texttt{C}.
+\item obtain \texttt{[21, 31, 41, 0]}.
+\end{itemize}
+\end{frame}
+\begin{frame}[fragile]
+\frametitle{Solution 3}
+\label{sec-9}
+
+\lstset{language=Python}
+\begin{lstlisting}
+In []:  C[1, 1:3]
+In []:  C[0:4, 0]
+In []:  C[1:5, 0]
+\end{lstlisting}
+\end{frame}
+\begin{frame}
+\frametitle{Question 4}
+\label{sec-10}
+
+  Obtain \texttt{[[23, 24], [33, -34]]} from \texttt{C}
+\end{frame}
+\begin{frame}[fragile]
+\frametitle{Solution 4}
+\label{sec-11}
+
+\lstset{language=Python}
+\begin{lstlisting}
+In []:  C[1:3, 2:4]
+\end{lstlisting}
+\end{frame}
+\begin{frame}
+\frametitle{Question 5}
+\label{sec-12}
+
+  Obtain the square in the center of the image
+\end{frame}
+\begin{frame}[fragile]
+\frametitle{Solution 5}
+\label{sec-13}
+
+\lstset{language=Python}
+\begin{lstlisting}
+In []: imshow(I[75:225, 75:225])
+\end{lstlisting}
+\end{frame}
+\begin{frame}[fragile]
+\frametitle{Question 6}
+\label{sec-14}
+
+  Obtain the following
+\lstset{language=Python}
+\begin{lstlisting}
+[[12, 0], [42, 0]]
+[[12, 13, 14], [0, 0, 0]]
+\end{lstlisting}
+\end{frame}
+\begin{frame}[fragile]
+\frametitle{Solution 6}
+\label{sec-15}
+
+\lstset{language=Python}
+\begin{lstlisting}
+In []: C[::3, 1::3]
+In []: C[::4, 1:4]
+\end{lstlisting}
+\end{frame}
+\begin{frame}
+\frametitle{Summary}
+\label{sec-16}
+
+  You should now be able to --
+\begin{itemize}
+\item Manipulate single \& multi dimensional arrays
+
+\begin{itemize}
+\item Access and change individual elements
+\item Access and change rows and columns
+\item Slice and stride on arrays
+\end{itemize}
+
+\item Read images into arrays and manipulate them.
+\end{itemize}
+\end{frame}
+\begin{frame}
+\frametitle{Thank you!}
+\label{sec-17}
+
+  \begin{block}{}
+  \begin{center}
+  This spoken tutorial has been produced by the
+  \textcolor{blue}{FOSSEE} team, which is funded by the 
+  \end{center}
+  \begin{center}
+    \textcolor{blue}{National Mission on Education through \\
+      Information \& Communication Technology \\ 
+      MHRD, Govt. of India}.
+  \end{center}  
+  \end{block}
+\end{frame}
+
+\end{document}