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+.. 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   :
+    Checklist OK?       : <put date stamp here, if 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 arrays, how to convert a list into an
+array and also why an array is preferred over lists. And array operations.
+
+.. #[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, it can have only one type of data
+type, either all integers, or strings, or float, and 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 are really fast in mathematical operations when compared to lists,
+it is at least 80 to 100 times faster than lists.
+
+.. #[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.
+
+I am assuming that you have your IPython interpreter running with the
+``-pylab`` option, so that you have the required modules loaded.
+
+.. #[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 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. Pause here and try to do it yourself before looking at
+the solution.
+
+.. #[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.]
+
+This is how we create two dimensional arrays.
+
+::
+
+    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.]
+
+Let us see an easy method of creating an array with elements 1 to 8.
+
+::
+
+    ar = arange(1,9)
+
+.. #[Puneeth: say, creating the same array as before. for some time I got
+.. confused .]
+
+And it created a single dimensional array of 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 order (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 object ``.shape``, let us
+check the shape of the arrays we have created so far,
+
+.. #[Puneeth: s/object/method ?]
+
+::
+
+    a1.shape
+
+``a1.shape`` object is a tuple, and since a1 is a single dimensional array,
+it returned a tuple (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.]
+
+{{{ 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 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,
+
+{{{ 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 string, though our
+first three elements were 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?]
+
+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.
+
+.. #[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 we
+want to create, and it generates an array with all elements zero.
+
+{{{ 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, how to create an array, converting a list to an array,
+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: