1 .. Objectives

     2 .. ----------

     3 

     4 .. At the end of this tutorial, you will be able to 

     5 

     6 .. 1. Saving plots using ``savefig()`` function.

     7 .. #. Saving plots in different formats.

     8 

     9 

    10 .. Prerequisites

    11 .. -------------

    12 

    13 ..   1. should have ``ipython`` and ``pylab`` installed. 

    14 ..   #. getting started with ``ipython``.

    15 ..   #. using plot command interactively.

    16      

    17 .. Author              : Anoop Jacob Thomas <anoop@fossee.in>

    18    Internal Reviewer   : 

    19    External Reviewer   :

    20    Checklist OK?       : <put date stamp here, if OK> [2010-10-05]

    21 

    22 

    23 =======

    24 Savefig

    25 =======

    26 

    27 {{{ Show the first slide }}}

    28 

    29 Hello and welcome to the tutorial saving plots.

    30 

    31 {{{ switch to next slide, outline slide }}}

    32 

    33 In this tutorial you will learn how to save plots using Python. And

    34 saving in different formats, and locating the file in the file system.

    35 

    36 {{{ switch to next slide, a sine wave}}}

    37 

    38 Start your IPython interpreter with the command ::

    39 

    40   ipython -pylab

    41 

    42 It will start your IPython interpreter with the required python

    43 modules for plotting and saving your plots.

    44 

    45 {{{ Open ipython }}}

    46 

    47 Now let us plot something, let us plot a sine wave from minus 3 pi to

    48 3 pi. Let us start by calculating the required points for the plot. It

    49 can be done using linspace as, ::

    50 

    51   x = linspace(-3*pi,3*pi,100)

    52 

    53 We have stored required points in x. Now let us plot the points using

    54 the statement ::

    55 

    56   plot(x,sin(x))

    57 

    58 {{{ Keep the plot open }}}

    59 

    60 Done! we have made a very basic sine plot, now let us see how to save

    61 the plot for future use so that you can embed the plot in your

    62 reports.

    63 

    64 {{{ switch to next slide, savefig() }}}

    65 

    66 {{{ Switch the focus to IPython interpreter window }}}

    67 

    68 For saving the plot, we will use ``savefig()`` function, and it has to be

    69 done with the plot window open. The statement is, ::

    70 

    71   savefig('/home/fossee/sine.png')

    72 

    73 Notice that ``savefig`` function takes one argument which is a string

    74 which is the filename. The last 3 characters after the ``.`` in the

    75 filename is the extension or type of the file which determines the

    76 format in which you want to save.

    77 

    78 {{{ Highlight the /home/fossee part using mouse movements }}}

    79 

    80 Also, note that we gave the full path or the absolute path to which we

    81 want to save the file.

    82 

    83 {{{ Highlight the .png part using mouse movements }}}

    84 

    85 Here I have used an extension ``.png`` which means i want to save the

    86 image as a PNG file.

    87 

    88 Now let us locate ``sine.png`` file saved. We saved the file to

    89 ``/home/fossee`` so let us navigate to ``/home/fossee`` using the

    90 file browser.

    91 

    92 {{{ Open the browser, navigate to /home/fossee and highlight the file

    93 sine.png }}}

    94 

    95 Yes, the file ``sine.png`` is here and let us check it.

    96 

    97 {{{ Open the file sine.png and show it for two-three seconds and then

    98 close it and return to IPython interpreter, make sure the plot window

    99 is still open, also don't close the file browser window }}}

   100 

   101 {{{ switch to next slide, More on savefig() }}}

   102 

   103 So in-order to save a plot, we use ``savefig`` function. ``savefig``

   104 can save the plot in many formats, such as pdf - portable document

   105 format, ps - post script, eps - encapsulated post script, svg -

   106 scalable vector graphics, png - portable network graphics which

   107 support transparency etc.

   108 

   109 .. #[[slide must give the extensions for the files - Anoop]]

   110 

   111 {{{ switch to next slide, exercise 1 }}}

   112 

   113 Let us now try to save the plot in eps format. ``eps`` stands for

   114 encapsulated post script, and it can be embedded in your latex

   115 documents. Pause here and try to figure it out yourself.

   116 

   117 {{{ Switch focus to the already open plot window }}}

   118 

   119 We still have the sine plot with us, and now let us save the plot as

   120 ``sine.eps``.

   121 

   122 {{{ switch to next slide, solution 1 }}}

   123 

   124 {{{ Switch focus to IPython interpreter }}}

   125 

   126 Now, We will save the plot using the function ``savefig`` ::

   127 

   128   savefig('/home/fossee/sine.eps')

   129 

   130 {{{ Switch focus to file browser window }}}

   131 

   132 Now let us go to ``/home/fossee`` and see the new file created.

   133 

   134 {{{ Highlight the file sine.eps with a single mouse click for 2

   135 seconds and then double click and open the file }}}

   136 

   137 Yes! the new file ``sine.eps`` is here.

   138 

   139 {{{ switch to next slide, exercise 2 }}}

   140 

   141 Now you may try saving the same in pdf, ps, svg formats.

   142 

   143 {{{ Switch to summary slide }}}

   144 

   145 This brings us to the end of this tutorial, in this tutorial we

   146 learned to save plots using the function ``savefig()``. Saving the

   147 plots in different formats and locating the files in the file system.

   148 

   149 {{{ switch to Thank you slide }}}

   150 

   151 Thank you!