1 Hello and welcome to the tutorial on creating simple plots using

     2 Python.This tutorial is presented by the Fossee group.  

     3 {{{ Show the Title Slide }}} 

     4 

     5 I hope you have IPython running on your computer.

     6 

     7 In this tutorial we will look at plot command and also how to study

     8 the plot using the UI.

     9 

    10 {{{ Show Outline Slide }}}

    11 

    12 Lets start ipython on your shell, type :: 

    13 

    14       $ipython -pylab

    15 

    16 

    17 Pylab is a python library which provides plotting functionality.It

    18 also provides many other important mathematical and scientific

    19 functions. After running IPython -pylab in your shell if at the top of

    20 the result of this command, you see something like ::

    21  

    22 

    23    `ERROR: matplotlib could NOT be imported!  Starting normal

    24       IPython.`

    25 

    26 

    27 {{{ Slide with Error written on it }}}

    28 

    29 Then you have to install matplotlib and run this command again.

    30 

    31 Now type in your ipython shell ::

    32 

    33              In[]: linpace?

    34 

    35 

    36 

    37 as the documentation says, it returns `num` evenly spaced samples,

    38 calculated over the interval start and stop.  To illustrate this, lets

    39 do it form 1 to 100 and try 100 points.  ::

    40 

    41            In[]: linspace(1,100,100)

    42 

    43 As you can see a sequence of numbers from 1 to 100 appears.

    44 

    45 Now lets try 200 points between 0 and 1 you do this by typing ::

    46 

    47 

    48             In[]: linspace(0,1,200)

    49 

    50 0 for start , 1 for stop and 200 for no of points.  In linspace 

    51 the start and stop points can be integers, decimals , or

    52 constants. Let's try and get 100 points between -pi to pi. Type ::

    53            

    54             In[]: p = linspace(-pi,pi,100)

    55 

    56 

    57 'pi' here is constant defined by pylab. Save this to the variable, p

    58 .

    59 

    60 If you now ::

    61      

    62 	   In[]: len(p)

    63 

    64 You will get the no. of points. len function gives the no of elements

    65 of a sequence.

    66 

    67 

    68 Let's try and plot a cosine curve between -pi and pi using these

    69 points.  Simply type :: 

    70 

    71 

    72        	  In[]: plot(p,cos(points))

    73 

    74 Here cos(points) gets the cosine value at every corresponding point to

    75 p.

    76 

    77 

    78 We can also save cos(points) to variable cosine and plot it using

    79 plot.::

    80 

    81            In[]: cosine=cos(points) 

    82 

    83 	   In[]: plot(p,cosine)

    84 

    85  

    86 

    87 Now do ::

    88        	 

    89 	   In[]: clf()

    90 

    91 this will clear the plot.

    92 

    93 This is done because any other plot we try to make shall come on the

    94 same drawing area. As we do not wish to clutter the area with

    95 overlaid plots , we just clear it with clf().  Now lets try a sine

    96 plot. ::

    97 

    98 

    99     	 In []: plot(p,sin(p))

   100 

   101 

   102 

   103  

   104 The Window on which the plot appears can be used to study it better.

   105 

   106 First of all moving the mouse around gives us the point where mouse

   107 points at.  

   108 

   109 Also we have some buttons the right most among them is

   110 for saving the file. 

   111 

   112 Just click on it specifying the name of the file.  We will save the plot 

   113 by the name sin_curve in pdf format.

   114 

   115 

   116 

   117 {{{ Action corelating with the words }}}

   118 

   119 As you can see I can specify format of file from the dropdown.

   120 

   121 Formats like png ,eps ,pdf, ps are available.  

   122 

   123 Left to the save button is the slider button to specify the margins.  

   124 

   125 {{{ Action corelating with the words  }}}

   126 

   127 Left to this is zoom button to zoom into the plot. Just specify the 

   128 region to zoom into.  

   129 The button left to it can be used to move the axes of the plot.  

   130 

   131 {{{ Action corelating with the words }}}

   132  

   133 The next two buttons with a left and right arrow icons change the state of the 

   134 plot and take it to the previous state it was in. It more or less acts like a

   135 back and forward button in the browser.  

   136 

   137 {{{ Action corelating with the words }}}

   138 

   139 The last one is 'home' referring to the initial plot.

   140 

   141 {{{ Action corelating with the words}}}

   142 

   143 

   144 

   145 {{{ Summary Slide }}}

   146 

   147 

   148 In this tutorial we have looked at 

   149 

   150 1. Starting Ipython with pylab 

   151 

   152 2. Using linspace function to create `num` equaly spaced points in a region.

   153 

   154 3. Finding length of sequnces using  len.

   155  

   156 4. Plotting mathematical functions using plot.

   157 

   158 4. Clearing drawing area using clf 

   159  

   160 5. Using the UI of plot for studying it better . Using functionalities like save , zoom , moving the plots on x and y axis 

   161 

   162 etc ..

   163  

   164 

   165 

   166 {{{ Show the "sponsored by FOSSEE" slide }}}

   167 

   168  

   169 

   170 This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India

   171 

   172  

   173 

   174  Hope you have enjoyed and found it useful.

   175 

   176  Thankyou

   177 

   178  

   179 

   180 Author              : Amit Sethi

   181 Internal Reviewer   :

   182 Internal Reviewer 2 :