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.. Objectives
.. ----------
.. At the end of this tutorial, you will be able to
.. 1. Save plots using ``savefig()`` function.
.. #. Save plots in different formats.
.. Prerequisites
.. -------------
.. 1. should have ``ipython`` and ``pylab`` installed.
.. #. getting started with ``ipython``.
.. #. using plot command interactively.
.. Author : Anoop Jacob Thomas <anoop@fossee.in>
Internal Reviewer : Puneeth
External Reviewer :
Language Reviewer : Bhanukiran
Checklist OK? : <10-11-2010, Anand, OK> [2010-10-05]
.. #[Puneeth: Quickref missing.]
=======
Savefig
=======
{{{ Show the first slide }}}
Hello and welcome to the tutorial saving plots.
{{{ switch to next slide, outline slide }}}
In this tutorial you will learn how to save plots using Python, saving
in different formats, and locating the file in the file system.
.. #[Puneeth: file-system is too technical.]
{{{ switch to next slide, a sine wave}}}
Start your IPython interpreter with the command ::
ipython -pylab
As you know, 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.
.. #[Puneeth: All this is known stuff. You don't have to elaborate so
.. much on it. Just say, let us plot sin function from -3 pi to 3
.. pi. Show the commands, and be done with it. ]
{{{ switch to next slide, savefig() }}}
{{{ 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 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.
.. #[Puneeth: removed mention of string]
.. #[[Anoop: I think this treatment is better :) ]]
{{{ 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 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 }}}
{{{ switch to next slide, More on savefig() }}}
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]]
{{{ switch to next slide, exercise 1 }}}
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. Pause here and try to figure it out yourself.
{{{ Switch focus to the already open plot window }}}
We still have the sine plot with us, and now let us save the plot as
``sine.eps``.
{{{ switch to next slide, solution 1 }}}
{{{ 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.
{{{ switch to next slide, exercise 2 }}}
Now you may try saving the same in pdf, ps, svg formats.
{{{ Switch to summary slide }}}
This brings us to the end of this tutorial, in this tutorial we
learned to save plots using the function ``savefig()``. Saving the
plots in different formats and locating the files in the file system.
{{{ switch to Thank you slide }}}
Thank you!
|
