--- a/getting_started_with_arrays.rst Sat Oct 09 02:59:42 2010 +0530
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,213 +0,0 @@
-.. 4.1 LO: getting started with arrays (2) [anoop]
-.. ------------------------------------------------
-.. * why arrays
-.. + speed - simply say
-.. + array level operations
-.. * creating arrays
-.. + direct data
-.. + list conversion
-.. + homogeneous
-.. + builtins - identitiy, zeros,
-.. * array operations
-.. + =+ - * /=
-
-===========================
-Getting started with Arrays
-===========================
-
-{{{ 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 arrays, how to convert a list
-into an array and also why an array is preferred over lists. And array
-operations.
-
-{{{ switch to next slide on overview of array }}}
-
-Arrays are homogeneous data structures, unlike lists, arrays cannot
-have heterogeneous data elements, that is, it can have only one type
-of data type, either all integers, or strings, or float, and not a
-mix.
-
-Arrays are really fast in mathematical operations when compared to
-lists, it is at least 80 to 100 times faster than lists.
-
-{{{ switch to the next slide, creating arrays }}}
-
-I am assuming that you have your IPython interpreter running with the
-``-pylab`` option, so that you have the required modules loaded.
-
-To create an array we will use the function ``array()`` as,
-::
-
- a1 = array([1,2,3,4])
-
-Notice that here we created a one dimensional array. Also notice the
-object we passed to create an array. Now let us see how to create a
-two dimensional array.
-::
-
- a2 = array([[1,2,3,4],[5,6,7,8]])
-
-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 order (2,2,4).
-
-{{{ switch to the next slide, shape of an array }}}
-
-To find the shape of an array we can use the object ``.shape``, let us
-check the shape of the arrays we have created so far,
-::
-
- a1.shape
-
-``a1.shape`` object is a tuple, and since a1 is a single dimensional
-array, it returned a tuple (4,).
-
-{{{ switch to the next slide, unsolved exercise 2 }}}
-
-Find out the shape of the other two arrays that we have created.
-
-{{{ Array can have only a single type of data }}}
-
-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 expected an error as previously I said that an array can have
-only homogeneous elements, but it didn't give an error. Let us check
-the values in the new array created. In your IPython terminal type,
-::
-
- a4
-
-Did you notice it,
-
-{{{ highlight all the array elements one by one using mouse
-movements }}}
-
-all the elements have been implicitly type casted as string, though
-our first three elements were integers.
-
-{{{ switch to the next slide, identity & zeros methods }}}
-
-An identity matrix is a square matrix in which all the diagonal
-elements are one and rest of the elements zero. We can create an
-identity matrix using the method ``identity()``.
-
-The function ``identity()`` takes an integer argument,
-::
-
- identity(3)
-
-As you can see the identity method returned a three by three square
-array with all the diagonal elements as one and the rest of the
-elements as zero.
-
-``zeros()`` function accepts a tuple, which is the order of the array
-we want to create, and it generates an array with all elements zero.
-
-{{{ switch to the next slide, problem statement of the 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, recap slide }}}
-
-So this brings us to the end of this tutorial, in this tutorial we covered basics of arrays, how to create an array, converting a list to an array, basic array operations etc.
-
-{{{ switch to next slide, thank you }}}
-
-Thank you!
-
-.. Author: Anoop Jacob Thomas <anoop@fossee.in>
- Reviewer 1:
- Reviewer 2:
- External reviewer: