# HG changeset patch
# User anoop
# Date 1284728931 -19800
# Node ID b7c47307e5101d68ca4f74dd47920f1c72bfccad
# Parent  b459053192f1c6e08033255d0e67b986ba981a53
added dictionaries, getting started with for, other_type_of_plots and savefig.

diff -r b459053192f1 -r b7c47307e510 dictionaries.rst
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dictionaries.rst	Fri Sep 17 18:38:51 2010 +0530
@@ -0,0 +1,177 @@
+.. 8.4 LO: dictionaries (2)
+.. ------------------------
+.. * empty 
+.. * filled 
+.. * accessing via keys 
+.. * .values(), .keys() 
+.. * in 
+.. * iteration
+
+============
+Dictionaries
+============
+
+{{{ show the welcome slide }}}
+
+Welcome to the spoken tutorial on dictionaries.
+
+{{{ switch to next slide, outline slide }}}
+
+In this tutorial, we will see how to create empty dictionaries, learn
+about keys and values of dictionaries. Checking for elements and
+iterating over elements.
+
+{{{ switch to next slide on overview of dictionaries }}}
+
+A dictionary in general, is designed to look up meanings of
+words. Similarly, Python dictionary is also designed to look up for a
+specific key and retrieve the corresponding value. Dictionaries are
+data structures that provide key-value mappings.  Dictionaries are
+similar to lists except that instead of the values having integer
+indexes, dictionaries have keys or strings as indexes.
+
+Before we can proceed, start your IPython interpreter with the
+``-pylab`` option.
+
+{{{ start ipython interpreter by issuing command ipython -pylab }}}
+
+Let us start by creating an empty dictionary, type the following in
+your IPython interpreter.
+::
+
+    mt_dict = {}    
+
+Notice that unlike lists curly braces are used define ``dictionary``,
+
+{{{ move the mouse over curly braces to grab attention }}}
+
+Now let us see how to create a filled dictionary,
+::
+
+    extensions = {'jpg' : 'JPEG Image', 'py' : 'Python script', 'html' : 'Html document', 'pdf' : 'Portable Document Format'}
+
+Notice that each key-value pair is separated by a comma
+
+{{{ move the mouse over the commas to grab attention }}}
+
+and each key and value are separated using a colon.
+
+{{{ move the mouse over the colon one by one to grab attention }}}
+
+Here, we defined four entries in the dictionary extensions. The keys
+are
+
+{{{ spell the keys letter by letter }}}
+
+jpg, py, html, and pdf.
+
+Simply type,
+::
+
+    extensions
+
+in the interpreter to see the content of the dictionary. Notice that
+in dictionaries the order cannot be predicted and you can see that the
+values are not in the order that we entered in.
+
+Like in lists, the elements in a dictionary can be accessed using the
+index, here the index is the key. Try,
+::
+
+    print extensions['jpg']
+
+It printed JPEG Image. And now try,
+::
+
+    print extensions['zip']
+
+Well it gave us an error, saying that the key 'zip' is not in the
+dictionary.
+
+Pause here for some time and try few more keys. Also try jpg in
+capital letters.
+
+{{{ switch to next slide, adding and deleting keys and values in
+dictionaries }}}
+
+Well that was about creating dictionaries, now how do we add or delete
+items. We can add new items into dictionaries as,
+::
+
+    extensions['cpp'] = 'C++ code'
+
+and delete items using the ``del`` keyword as,
+::
+
+    del extension['pdf']
+
+Let us check the content of the dictionary now,
+::
+
+    extensions
+
+So the changes have been made. Now let us try one more thing,
+::
+
+    extensions['cpp'] = 'C++ source code'
+    extensions
+
+As you can see, it did not add a new thing nor gave an error, but it
+simply replaces the existing value with the new one.
+
+Now let us learn how to check if a particular key is present in the
+dictionary. For that we can use ``in``,
+::
+
+    'py' in extensions
+    'odt' in extensions
+
+So in short it will return ``True`` if the key is found in the
+dictionary, and will return ``False`` if key is not present. Note that
+we can check only for container-ship of keys in dictionaries and not
+values.
+
+{{{ switch to next slide, Retrieve keys and values }}}
+
+Now let us see how to retrieve the keys and values. We can use the
+method ``keys()`` for getting a list of the keys in a particular
+dictionary and the method ``values()`` for getting a list of
+values. Let us try them,
+::
+
+    extensions.keys()
+
+It returned the ``list`` of keys in the dictionary extensions. And now
+the other one,
+::
+
+    extensions.values()
+
+It returned the ``list`` of values in the dictionary.
+
+{{{ switch to next slide, problem statement for the next solved
+exercise }}}
+
+Now let us try to print the data in the dictionary. We can use ``for``
+loop to iterate.
+::
+
+    for each in extensions.keys():
+        print each, "-->", extensions[each]
+
+
+{{{ switch to next slide, recap }}}
+
+This brings us to the end of this tutorial, we learned dictionaries
+and saw how to create an empty dictionary, build a dictionary with
+some data in it, adding data, ``keys()`` and ``values()`` methods, and
+iterating over the dictionaries.
+
+{{{ switch to next slide, thank you slide }}}
+
+Thank you!
+
+..  Author: Anoop Jacob Thomas <anoop@fossee.in>
+    Reviewer 1:
+    Reviewer 2:
+    External reviewer:
diff -r b459053192f1 -r b7c47307e510 getting_started_with_for.rst
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/getting_started_with_for.rst	Fri Sep 17 18:38:51 2010 +0530
@@ -0,0 +1,217 @@
+.. 3.2 LO: getting started with =for= (2) [anoop] 
+.. -----------------------------------------------
+.. * blocks in python 
+..   + (indentation) 
+.. * blocks in ipython 
+..   + ... prompt 
+..   + hitting enter 
+.. * =for= with a list 
+.. * =range= function 
+
+=============================
+Getting started with for loop
+=============================
+
+{{{ show welcome slide }}}
+
+Hello and welcome to the tutorial getting started with ``for`` loop. 
+
+{{{ switch to next slide, outline slide }}}
+
+In this tutorial we will see ``for`` loops in python, and also cover
+the basics of indenting code in python.
+
+{{{ switch to next slide, about whitespaces }}}
+
+In Python whitespace is significant, and the blocks are visually
+separated rather than using braces or any other mechanisms for
+defining blocks. And by this method Python forces the programmers to
+stick on to one way of writing or beautifying the code rather than
+debating over where to place the braces. This way it produces uniform
+code than obscure or unreadable code.
+
+A block may be defined by a suitable indentation level which can be
+either be a tab or few spaces. And the best practice is to indent the
+code using four spaces.
+
+Now let us move straight into ``for`` loop.
+
+{{{ switch to next slide,  problem statement of exercise 1 }}}
+
+Write a for loop which iterates through a list of numbers and find the
+square root of each number. Also make a new list with the square roots
+and print it at the end.
+::
+
+    numbers are 1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916
+
+For the problem, first we need to create a ``list`` of numbers and
+then iterate over the list and find the square root of each element in
+it. And let us create a script, rather than typing it out in the
+interpreter itself. Create a script called list_roots.py and type the
+following.
+
+{{{ open the text editor and paste the following code there }}}
+::
+
+    numbers = [1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916]
+    square_roots = []
+    for each in numbers:
+        sq_root = sqrt(each)
+        print "Square root of", each, "is", sq_root
+        square_roots.append(sq_root)
+    print 
+    print square_roots
+
+{{{ save the script }}}
+
+Now save the script, and run it from your IPython interpreter. I
+assume that you have started your IPython interpreter using ``-pylab``
+option.
+
+Run the script as,
+::
+
+    %run -i list_roots.py
+
+{{{ run the script }}}
+
+So that was easy! We didn't have to find the length of the string nor
+address of each element of the list one by one. All what we did was
+iterate over the list element by element and then use the element for
+calculation. Note that here we used three variables. One the variable
+``numbers``, which is a list, another one ``each``, which is the
+element of list under consideration in each cycle of the ``for`` loop,
+and then a variable ``sq_root`` for storing the square root in each
+cycle of the ``for`` loop. The variable names can be chosen by you.
+
+{{{ show the script which was created }}}
+
+Note that three lines after ``for`` statement, are indented using four
+spaces.
+
+{{{ highlight the threee lines after for statement }}}
+
+It means that those three lines are part of the for loop. And it is
+called a block of statements. And the seventh line or the immediate
+line after the third line in the ``for`` loop is not indented, 
+
+{{{ highlight the seventh line - the line just after for loop }}}
+
+it means that it is not part of the ``for`` loop and the lines after
+that doesn't fall in the scope of the ``for`` loop. Thus each block is
+separated by the indentation level. Thus marking the importance of
+white-spaces in Python.
+
+{{{ switch to the slide which shows the problem statement of the first
+problem to be tried out }}}
+
+Now a question for you to try, from the given numbers make a list of
+perfect squares and a list of those which are not. The numbers are,
+::
+    
+    7225, 3268, 3364, 2966, 7056, 5625, 729, 5547, 7056, 576, 2916
+
+{{{ switch to next slide, problem statement of second problem in
+solved exercie}}}
+
+Now let us try a simple one, to print the square root of numbers in
+the list. And this time let us do it right in the IPython
+interpreter. 
+
+{{{ switch focus to the IPython interpreter }}}
+
+So let us start with making a list. Type the following
+::
+
+    numbers = [1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916]
+    for each in numbers:
+
+and now you will notice that, as soon as you press the return key
+after for statement, the prompt changes to four dots and the cursor is
+not right after the four dots but there are four spaces from the
+dots. The four dots tell you that you are inside a block. Now type the
+rest of the ``for`` loop,
+::
+
+        sq_root = sqrt(each)
+        print "Square root of", each, "is", sq_root
+
+Now we have finished the statements in the block, and still the
+interpreter is showing four dots, which means you are still inside the
+block. To exit from the block press return key or the enter key twice
+without entering anything else. It printed the square root of each
+number in the list, and that is executed in a ``for`` loop.
+
+Now, let us generate the multiplication table of 10 from one to
+ten. But this time let us try it in the vanilla version of Python
+interpreter.
+
+Start the vanilla version of Python interpreter by issuing the command
+``python`` in your terminal.
+
+{{{ open the python interpreter in the terminal using the command
+python to start the vanilla Python interpreter }}}
+
+Start with,
+::
+    
+    for i in range(1,11):
+
+and press enter once, and we will see that this time it shows four
+dots, but the cursor is close to the dots, so we have to intend the
+block. So enter four spaces there and then type the following
+::
+    
+    
+        print "10 *",i,"=",i*10
+
+Now when we hit enter, we still see the four dots, to get out of the
+block type enter once.
+
+Okay! so the main thing here we learned is how to use Python
+interpreter and IPython interpreter to specify blocks. But while we
+were generating the multiplication table we used something new,
+``range()`` function. ``range()`` is an inbuilt function in Python
+which can be used to generate a ``list`` of integers from a starting
+range to an ending range. Note that the ending number that you specify
+will not be included in the ``list``.
+
+Now, let us print all the odd numbers from 1 to 50. Let us do it in
+our IPython interpreter for ease of use.
+
+{{{ switch focus to ipython interpreter }}}
+
+{{{ switch to next slide, problem statement of the next problem in
+solved exercises }}}
+
+Print the list of odd numbers from 1 to 50. It will be better if
+you can try it out yourself.
+
+It is a very trivial problem and can be solved as,
+::
+
+    print range(1,51,2)
+
+This time we passed three parameters to ``range()`` function unlike
+the previous case where we passed only two parameters. The first two
+parameters are the same in both the cases. The first parameter is the
+starting number of the sequence and the second parameter is the end of
+the range. Note that the sequence doesn't include the ending
+number. The third parameter is for stepping through the sequence. Here
+we gave two which means we are skipping every alternate element.
+
+{{{ switch to next slide, recap slide }}}
+
+Thus we come to the end of this tutorial. We learned about blocks in
+Python, indentation, blocks in IPython, for loop, iterating over a
+list and then the ``range()`` function.
+
+{{{ switch to next slide, thank you slide }}}
+
+Thank you!
+
+..  Author: Anoop Jacob Thomas <anoop@fossee.in>
+    Reviewer 1:
+    Reviewer 2:
+    External reviewer:
diff -r b459053192f1 -r b7c47307e510 other_type_of_plots.rst
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/other_type_of_plots.rst	Fri Sep 17 18:38:51 2010 +0530
@@ -0,0 +1,220 @@
+.. 2.4 LO: other types of plots (3) [anoop] 
+.. -----------------------------------------
+.. * scatter 
+.. * pie chart 
+.. * bar chart 
+.. * log 
+.. * illustration of other plots, matplotlib help
+
+===================
+Other type of plots
+===================
+
+{{{ show the first slide }}}
+
+Hello and welcome to the tutorial other type of plots.
+
+{{{ show the outline slide }}}
+
+In this tutorial we will cover scatter plot, pie chart, bar chart and
+log plot. We will also see few other plots and also introduce you to
+the matplotlib help.
+
+
+Let us start with scatter plot. 
+
+{{{ switch to the next slide }}}
+
+In a scatter plot, the data is displayed as a collection of points,
+each having the value of one variable determining the position on the
+horizontal axis and the value of the other variable determining the
+position on the vertical axis. This kind of plot is also called a
+scatter chart, scatter diagram and scatter graph.
+
+Before we proceed further get your IPython interpreter running with
+the ``-pylab`` option. Start your IPython interpreter as
+::
+
+    ipython -pylab
+
+{{{ open the ipython interpreter in the terminal using the command
+ipython -pylab }}}
+
+{{{ switch to the next slide having the problem statement of first
+exercise }}}
+
+Now, let us plot a scatter plot showing the percentage profit of company A
+from the year 2000-2010. The data for the same is available in the
+file ``company-a-data.txt``. 
+
+{{{ open the file company-a-data.txt and show the content }}}
+
+The data file has two lines with a set of values in each line, the
+first line representing years and the second line representing the
+profit percentages.
+
+{{{ close the file and switch to the terminal }}}
+
+To product the scatter plot first we need to load the data from the
+file using ``loadtxt``. We learned in one of the previous sessions,
+and it can be done as ::
+
+    year,profit = loadtxt('/home/fossee/other-plot/company-a-data.txt',dtype=type(int()))
+
+Now in-order to generate the scatter graph we will use the function 
+``scatter()`` 
+::
+
+	scatter(year,profit)
+
+Notice that we passed two arguments to ``scatter()`` function, first
+one the values in x-coordinate, year, and the other the values in
+y-coordinate, the profit percentage.
+
+{{{ switch to the next slide which has the problem statement of
+problem to be tried out }}}
+
+Now here is a question for you to try out, plot the same data with red
+diamonds. 
+
+**Clue** - *try scatter? in your ipython interpreter* 
+
+.. scatter(year,profit,color='r',marker='d')
+
+Now let us move on to pie chart.
+
+{{{ switch to the slide which says about pie chart }}}
+
+A pie chart or a circle graph is a circular chart divided into
+sectors, illustrating proportion.
+
+{{{ switch to the slide showing the problem statement of second
+exercise question }}}
+
+Plot a pie chart representing the profit percentage of company A, with
+the same data from file ``company-a-data.txt``. So let us reuse the
+data we have loaded from the file previously.
+
+We can plot the pie chart using the function ``pie()``.
+::
+
+   pie(profit,labels=year)
+
+Notice that we passed two arguments to the function ``pie()``. The
+first one the values and the next one the set of labels to be used in
+the pie chart.
+
+{{{ switch to the next slide which has the problem statement of
+problem to be tried out }}}
+
+Now here is a question for you to try out, plot a pie chart with the
+same data with colors for each wedges as white, red, black, magenta,
+yellow, blue, green, cyan, yellow, magenta and blue respectively.
+
+**Clue** - *try pie? in your ipython interpreter* 
+
+.. pie(t,labels=s,colors=('w','r','k','m','y','b','g','c','y','m','b'))
+
+{{{ switch to the slide which says about bar chart }}}
+
+Now let us move on to bar chart. A bar chart or bar graph is a chart
+with rectangular bars with lengths proportional to the values that
+they represent.
+
+{{{ switch to the slide showing the problem statement of third
+exercise question }}}
+
+Plot a bar chart representing the profit percentage of company A, with
+the same data from file ``company-a-data.txt``. 
+
+So let us reuse the data we have loaded from the file previously.
+
+We can plot the bar chart using the function ``bar()``.
+::
+
+   bar(year,profit)
+
+Note that the function ``bar()`` needs at least two arguments one the
+values in x-coordinate and the other values in y-coordinate which is
+used to determine the height of the bars.
+
+{{{ switch to the next slide which has the problem statement of
+problem to be tried out }}}
+
+Now here is a question for you to try, plot a bar chart which is not
+filled and which is hatched with 45\ :sup:`o` slanting lines as shown
+in the image in the slide.
+
+**Clue** - *try bar? in your ipython interpreter* 
+
+.. bar(year,profit,fill=False,hatch='/')
+
+{{{ switch to the slide which says about bar chart }}}
+
+Now let us move on to log-log plot. A log-log graph or log-log plot is
+a two-dimensional graph of numerical data that uses logarithmic scales
+on both the horizontal and vertical axes. Because of the nonlinear
+scaling of the axes, a function of the form y = ax\ :sup:`b` will
+appear as a straight line on a log-log graph
+
+{{{ switch to the slide showing the problem statement of fourth
+exercise question }}}
+
+
+Plot a `log-log` chart of y=5*x\ :sup:`3` for x from 1-20.
+
+Before we actually plot let us calculate the points needed for
+that. And it could be done as,
+::
+
+    x = linspace(1,20,100)
+    y = 5*x**3
+
+Now we can plot the log-log chart using ``loglog()`` function,
+::
+
+    loglog(x,y)
+
+To understand the difference between a normal ``plot`` and a ``log-log
+plot`` let us create another plot using the function ``plot``.
+::
+
+    figure(2)
+    plot(x,y)
+
+{{{ show both the plots side by side }}}
+
+So that was ``log-log() plot``.
+
+{{{ switch to the next slide which says: "How to get help on
+matplotlib online"}}}
+
+Now we will see few more plots and also see how to access help of
+matplotlib over the internet.
+
+Help about matplotlib can be obtained from
+matplotlib.sourceforge.net/contents.html
+
+.. #[[Anoop: I am not so sure how to do the rest of it, so I guess we
+   can just browse through the side and tell them few. What is your
+   opinion??]]
+
+Now let us see few plots from
+matplotlib.sourceforge.net/users/screenshots.html
+
+{{{ browse through the site quickly }}}
+
+{{{ switch to recap slide }}}
+
+Now we have come to the end of this tutorial. We have covered scatter
+plot, pie chart, bar chart, log-log plot and also saw few other plots
+and covered how to access the matplotlib online help.
+
+{{{ switch to the thank you slide }}}
+
+Thank you!
+
+..  Author: Anoop Jacob Thomas <anoop@fossee.in>
+    Reviewer 1:
+    Reviewer 2:
+    External reviewer:
diff -r b459053192f1 -r b7c47307e510 savefig.rst
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/savefig.rst	Fri Sep 17 18:38:51 2010 +0530
@@ -0,0 +1,111 @@
+=======
+Savefig
+=======
+
+Hello and welcome to the tutorial. In this tutorial you will learn how
+to save plots using Python.
+
+Start your IPython interpreter with the command ::
+
+  ipython -pylab
+
+It will start your IPython interpreter with the required python
+modules for plotting and saving your plots.
+
+{{{ Open ipython }}}
+
+Now let us plot something, let us plot a sine wave from minus 3 pi to
+3 pi. Let us start by calculating the required points for the plot. It
+can be done using linspace as, ::
+
+  x = linspace(-3*pi,3*pi,100)
+
+We have stored required points in x. Now let us plot the points using
+the statement ::
+
+  plot(x,sin(x))
+
+{{{ Keep the plot open }}}
+
+Done! we have made a very basic sine plot, now let us see how to save
+the plot for future use so that you can embed the plot in your
+reports.
+
+{{{ Switch the focus to IPython interpreter window }}}
+
+For saving the plot, we will use savefig function, and it has to be
+done with the plot window open. The statement is, ::
+
+  savefig('/home/fossee/sine.png')
+
+Notice that ``savefig`` function takes one argument which is a string
+which is the filename. The last 3 characters after the ``.`` in the
+filename is the extension or type of the file which determines the
+format in which you want to save.
+
+{{{ Highlight the /home/fossee part using mouse movements }}}
+
+Also, note that we gave the full path or the absolute path to which we
+want to save the file.
+
+{{{ Highlight the .png part using mouse movements }}}
+
+Here I have used an extension ``.png`` which means i want to save the
+image as a PNG file.
+
+Now let us locate ``sine.png`` file saved. We saved the file to
+``/home/fossee`` so let us navigate to ``/home/fossee`` using the
+file browser.
+
+{{{ Open the browser, navigate to /home/fossee and highlight the file
+sine.png }}}
+
+Yes, the file ``sine.png`` is here and let us check the it.
+
+{{{ Open the file sine.png and show it for two-three seconds and then
+close it and return to IPython interpreter, make sure the plot window
+is still open, also don't close the file browser window }}}
+
+So in-order to save a plot, we use ``savefig`` function. ``savefig``
+can save the plot in many formats, such as pdf - portable document
+format, ps - post script, eps - encapsulated post script, svg -
+scalable vector graphics, png - portable network graphics which
+support transparency etc.
+
+#[slide must give the extensions for the files - Anoop]
+
+Let us now try to save the plot in eps format. ``eps`` stands for
+encapsulated post script, and it can be embedded in your latex
+documents.
+
+{{{ Switch focus to the already open plot window }}}
+
+We still have the old sine plot with us, and now let us save the plot
+as ``sine.eps``.
+
+{{{ Switch focus to IPython interpreter }}}
+
+Now, We will save the plot using the function ``savefig`` ::
+
+  savefig('/home/fossee/sine.eps')
+
+{{{ Switch focus to file browser window }}}
+
+Now let us go to ``/home/fossee`` and see the new file created.
+
+{{{ Highlight the file sine.eps with a single mouse click for 2
+seconds and then double click and open the file }}}
+
+Yes! the new file ``sine.eps`` is here.
+
+Now you may try saving the same in pdf, ps, svg formats.
+
+Let us review what we have learned in this session! We have learned to
+save plots in different formats using the function ``savefig()``.
+
+Thank you!
+
+..  Author: Anoop Jacob Thomas <anoop@fossee.in>
+    Reviewer 1:
+    Reviewer 2:
+    External reviewer: