--- a/getting-started-with-arrays/script.rst Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,343 +0,0 @@
-.. Objectives
-.. ----------
-
-.. At the end of this tutorial, you will be able to
-
-.. 1. Create arrays using data
-.. #. Create arrays from lists
-.. #. Basic array operations
-.. #. Creating identity matrix using ``identity()`` function.
-.. #. Learn about ``zeros()``, ``zeros_like()``, ``ones()``,
- ``ones_like()`` functions.
-
-.. Prerequisites
-.. -------------
-
-.. 1. should have ``ipython`` and ``pylab`` installed.
-.. #. getting started with ``ipython``.
-.. #. getting started with lists.
-
-.. Author: Anoop Jacob Thomas <anoop@fossee.in>
- Internal Reviewer : Puneeth
- External Reviewer :
- Language Reviewer : Bhanukiran
- Checklist OK? : <11-11-2010,Anand, OK > [2010-10-05]
-
-===========================
-Getting started with Arrays
-===========================
-
-.. #[Puneeth: Prerequisites and Objectives are missing. Fill them in]
-
-{{{ show the welcome slide }}}
-
-Welcome to the spoken tutorial on getting started with arrays.
-
-{{{ switch to next slide, outline slide }}}
-
-In this tutorial, we will learn about the data structure called an array, how to convert
-a list into an array, operations on arrays and also why an array is preferred
-to lists.
-
-.. #[Puneeth: Fix the grammar above.]
-
-{{{ switch to next slide on overview of array }}}
-
-Arrays are homogeneous data structures. Unlike lists, arrays cannot have
-heterogeneous data elements, that is, they can have only one type of data
-as their entries, be them all integers, strings, or maybe floats, but not a mix.
-
-.. #[Puneeth: Use multiple short sentences, rather than one long sentence
- I would've written something like this.
-
- Unlike lists, arrays are homogeneous data structures. They can have only
- type of data, ....]
-
-Arrays of a given length are comparatively much faster in mathematical
-operations than lists of the same length, because of the fact that they are
-homogeneous data structures.
-
-.. #[Puneeth: For what size of an array is that the comparison?
-
-{{{ switch to the next slide, creating arrays }}}
-
-Now let us see how to create arrays.
-
-Run your IPython interpreter with ``-pylab`` option, to load the required
-modules to work with arrays.
-{{{ take terminal and run the following command }}}
-::
-
- ipython -pylab
-
-.. #[Puneeth: 'I am assuming' doesn't sound right. Ask them to open if it
-.. is not open?]
-
-To create an array we will use the function ``array()`` as,
-
-::
-
- a1 = array([1,2,3,4])
-
-Notice that we created a one dimensional array here. Also notice the object
-we passed to create an array. We passed a list to create an array.
-
-Now let us see how to create a two dimensional array. Pause here and try to
-do it yourself before looking at the solution.
-
-{{{ switch to next slide, creating two dimensional arrays }}}
-
-.. #[Puneeth: I don't think this question can be solved by an average
-.. viewer. Questions during the tutorial, should generally be to re-iterate
-.. concepts learnt? ]
-
-.. #[Puneeth: Also, you didn't even point out that we are converting a
-.. list, using the ``array`` function. Bring the later section about
-.. converting a list, here. A separate section is not necessary, IMHO.]
-
-We create two dimensional array by converting a list of lists to an array
-as,
-
-::
-
- a2 = array([[1,2,3,4],[5,6,7,8]])
-
-.. #[Puneeth: Again, you could explain a bit about the fact that we are
-.. converting a list of lists.]
-
-Now let us use ``arange()`` function to create the same array as before.
-
-::
-
- ar = arange(1,9)
-
-.. #[Puneeth: say, creating the same array as before. for some time I got
-.. confused .]
-
-And we obtained a one dimensional array with elements from 1 to 8.
-
-::
-
- print ar
-
-.. #[Puneeth: be consistent with voice. say, we obtained... or something.]
-
-And how can we make it a two dimensional array of order 2 by 4? Pause here
-and try to do it yourself, try ``ar.tab`` and find a suitable method for
-that.
-
-{{{ switch to next slide, reshape() method }}}
-
-We can use the function ``reshape()`` for that purpose and it can be done
-as,
-
-::
-
- ar.reshape(2,4)
- ar.reshape(4,2)
- ar = ar.reshape(2,4)
-
-{{{ switch to next slide, creating array from list}}}
-
-Now, let us see how to convert a list object to an array. As you have
-already seen, in both of the previous statements we have passed a list, so
-creating an array can be done so, first let us create a list ``l1``
-
-::
-
- l1 = [1,2,3,4]
-
-Now we can convert the list to an array as,
-
-::
-
- a3 = array(l1)
-
-
-{{{ switch to the next slide, problem statement of unsolved exercise 1 }}}
-
-Create a three dimensional array of the shape (2,2,4).
-
-.. #[Puneeth: s/order/shape or size ?]
-
-{{{ switch to the next slide, shape of an array }}}
-
-To find the shape of an array we can use the method ``.shape``, let us
-check the shape of the arrays we have created so far,
-
-.. #[Puneeth: s/object/method ?]
-
-::
-
- a2.shape
-
-``a2.shape`` object is a tuple, and it returned a tuple (2, 4).
-
-.. #[Puneeth: first show a 2D array, so that it becomes easier to explain.
-.. Also, the word ``tuple`` need not be mentioned. ]
-
-{{{ switch to the next slide, unsolved exercise 2 }}}
-
-Find out the shape of the other arrays that we have created.
-
-.. #[Puneeth: solution missing.]
-
-It can be done as,
-::
-
- a1.shape
- a3.shape
- ar.shape
-
-{{{ Array can have only a single type of data }}}
-
-.. #[Puneeth: I guess, this whole section can be skipped. If you want to
-.. keep this, just briefly mention that arrays are homogeneous in the
-.. intro, don't explain it there.]
-
-Now let us try to create a new array with a mix of elements and see what
-will happen,
-
-::
-
- a4 = array([1,2,3,'a string'])
-
-Well, we would expect an error as it has been previously mentioned that arrays handle
-elements with the same datatype, but it didn't raise an error. Let us check the values
-in the new array created. In your IPython terminal type,
-::
-
- a4
-
-Did you notice it,
-
-{{{ switch to next slide, implicit type casting }}}
-
-.. #[Puneeth: typecasting may be unnecessary. (Also too advanced?) an
-.. average guy wouldn't use arrays with strings.]
-
-.. #[Puneeth: You may want to mention that float is the default dtype.]
-
-{{{ highlight all the array elements one by one using mouse movements }}}
-
-all the elements have been implicitly type casted as strings, though our
-first three elements were meant to be integers.
-
-.. #[Puneeth: when I type a4 it says some ``dtype`` etc. I don't understand
-.. what it is, can you explain? ;)]
-
-{{{ switch to the next slide, identity & zeros methods }}}
-
-.. #[Puneeth: something needs to motivate this. why are we suddenly talking
-.. of an identity matrix?]
-
-Now let us see how to create an identity matrix of a given size, that is a
-two-dimensional array in which all the diagonal elements are ones and rest of the
-elements are zeros. We can create an identity matrix using the function
-``identity()``.
-
-The function ``identity()`` takes an integer argument which specifies the
-size of the desired matrix,
-
-::
-
- identity(3)
-
-As you can see the identity function returned a three by three square matrix
-with all the diagonal elements as ones and the rest of the elements as zeros.
-
-.. #[Puneeth: You say array here, matrix there -- it's a bit messed up.
-.. Clarify, explicitly.]
-
-``zeros()`` function accepts a tuple, which is the order of the array that we
-want to create, and it generates an array with all elements as zeros.
-
-{{{ switch to the next slide, problem statement of solved exercise 1 }}}
-
-Let us creates an array of the order four by five with all the elements
-zero. We can do it using the method zeros, ::
-
- zeros((4,5))
-
-Notice that we passed a tuple to the function zeros.
-
-{{{ switch to next slide, learning exercise }}}
-
-We learned two functions ``identity()`` and ``zeros()``, find out more
-about the functions ``zeros_like()``, ``ones()``, ``ones_like()``.
-
-{{{ switch to next slide, array operations }}}
-
-Try the following, first check the value of a1,
-::
-
- a1
-
-``a1`` is a single dimensional array, and now try,
-::
-
- a1 * 2
-
-It returned a new array with all the elements multiplied by 2.
-::
-
- a1
-
-note that the value of a1 still remains the same.
-
-Similarly with addition,
-::
-
- a1 + 2
-
-it returns a new array, with all the elements summed with two. But
-again notice that the value of a1 has not been changed.
-::
-
- a1
-
-You may change the value of a1 by simply assigning the newly returned
-array as,
-::
-
- a1 += 2
-
-Notice the change in elements of a,
-::
-
- a
-
-We can use all the mathematical operations with arrays, Now let us try this
-::
-
- a1 = array([1,2,3,4])
- a2 = array([1,2,3,4])
- a1 + a2
-
-Returns an array with element by element addition,
-::
-
- a1 * a2
-
-Returns an array with element by element multiplication, notice that it
-does not perform matrix multiplication.
-
-{{{ switch to next slide, summary slide }}}
-
-So this brings us to the end of this tutorial, in this tutorial we covered
-basics of arrays, learned how to create an array, saw how to convert a list
-to an array, and basic array operations etc.
-
-.. #[Puneeth: s/how to create an array/creating an array]
-
-{{{ switch to next slide, thank you }}}
-
-Thank you!
-
-..
- Local Variables:
- mode: rst
- indent-tabs-mode: nil
- sentence-end-double-space: nil
- fill-column: 75
- End: