1 Hello friends and welcome to the tutorial on Embellishing Plots

     2 

     3 {{{ Show the slide containing title }}}

     4 

     5 {{{ Show the slide containing the outline slide }}}

     6 

     7 In this tutorial, we shall look at how to modify the colour, thickness and 

     8 linestyle of the plot. We shall then learn how to add title to the plot and 

     9 then look at adding labels to x and y axes. we shall also look at adding 

    10 annotations to the plot.

    11 

    12 Let us start ipython with pylab loaded, by typing::

    13 

    14     ipython -pylab

    15 

    16 on the terminal

    17 

    18 {{{ shit to terminal and type ipython -pylab }}}

    19 

    20 We shall first make a simple plot and start with decorating it.::

    21 

    22     x = linspace(-2, 4, 20)

    23     plot(x, sin(x))

    24 

    25 As you can see, the colour and thickness of line as decided by pylab. It would

    26 be nice if we could control these parameters in the plot. This is possible by

    27 passing additional arguments to the plot command.

    28 

    29 The second argument that we shall be passing is colour. We shall first clear

    30 the figure and plot the same in red colour.Hence::

    31 

    32     clf()

    33     plot(x, sin(x), 'r')

    34 

    35 Plots the same curve but now in red colour.

    36 

    37 To alter the thickness of the line, we use the =linewidth= argument in the plot

    38 command.Hence::

    39 

    40     plot(x, cos(x), linewidth=2)

    41 

    42 produces a plot with a thicker line.

    43 

    44 {{{ Show the plot and compare the sin and cos plots }}}

    45 

    46 {{{ Pause here and try out the following exercises }}}

    47 

    48 %% 1 %% Plot sin(x) in blue colour and with linewidth as 3

    49 

    50 {{{ continue from paused state }}}

    51 

    52 A combination of colour and linewidth would do the job for us. Hence::

    53 

    54     plot(x, sin(x), 'b', linewidth=3)

    55 

    56 produces the required plot

    57 

    58 #[Nishanth]: I could not think of a SIMPLE recipe approach for introducing

    59              linestyle. Hence the naive approach.

    60 

    61 Occasionally we would also want to alter the style of line. Sometimes all we

    62 want is just a bunch of points not joined. This is possible by passing the

    63 linestyle argument along with or instead of the colour argument.Hence::

    64 

    65     clf()

    66     plot(x, sin(x), '.')

    67 

    68 produces a plot with only points.

    69 

    70 To produce the same plot but now in blue colour, we do::

    71 

    72     clf()

    73     plot(x, sin(x), 'b.')

    74 

    75 Other available options can be seen in the documentation of plot.::

    76 

    77     plot?

    78 

    79 {{{ Run through the documentation and show the options available }}}

    80 

    81 {{{ Pause here and try out the following exercises }}}

    82 

    83 %% 2 %% Plot the sine curve with green filled circles.

    84 

    85 {{{ continue from paused state }}}

    86 

    87 All we have to do is use a combination of linestyle and colour to acheive this.

    88 Hence::

    89 

    90     clf()

    91     plot(x, cos(x), 'go')

    92 

    93 produces the required plot.

    94 

    95 {{{ Pause here and try out the following exercises }}}

    96 

    97 %% 3 %% Produce a plot of tangent curve with red dashed line and linewidth 3

    98 

    99 {{{ continue from paused state }}}

   100 

   101 Now that we know how to produce a bare minimum plot with colour, style and

   102 thickness of our interest, we shall look at decorating the plot.

   103 

   104 Let us start with a plot of the function -x^2 + 4x - 5.::

   105 

   106     plot(x, -x*x + 4*x - 5, 'r', linewidth=2)

   107 

   108 {{{ Show the plot window and switch back to terminal }}}

   109 

   110 We now have the plot in a colour and linewidth of our interest. As you can see,

   111 the figure does have any description describing the plot.

   112 

   113 We will now add a title to the plot by using the =title= command.::

   114 

   115     title("Parabolic function -x^2+4x-5") 

   116 

   117 {{{ Show the plot window and point to the title }}}

   118 The figure now has a title which describes what the plot is.

   119 The =title= command as you can see, takes a string as argument and set the

   120 title accordingly.

   121 

   122 The formatting in title is messed and it does not look clean. You can imagine

   123 what would be the situation if there were fractions and more complex functions

   124 like log and exp. Wouldn't it be good if there was LaTex like formatting.

   125 

   126 That is also possible by adding a $ sign before and after the part of the 

   127 string that should be LaTex style.

   128 

   129 for instance, we can use::

   130 

   131     title("Parabolic function $-x^2+4x-5$")

   132 

   133 and we get the polynomial formatted properly.

   134 

   135 {{{ Pause here and try out the following exercises }}}

   136 

   137 %% 4 %% Change the title of the figure such that the whole title is formatted

   138         in LaTex style

   139 

   140 {{{ continue from the paused state }}}

   141 

   142 The solution is to enclose the whole string in between $. Hence,::

   143 

   144     title("$Parabolic function -x^2+4x-5$")

   145 

   146 gives a title that looks neatly formatted.

   147 

   148 Although we have title, the plot is not complete without labelling x and y

   149 axes. Hence we shall label x-axis to "x" and y-axis to "f(x)"::

   150 

   151     xlabel("x")

   152 

   153 {{{ Switch to plot window and show the xlabel }}}

   154 

   155 As you can see, =xlabel= command takes a string as argument, similar to the

   156 =title= command and sets it to x-axis.

   157 

   158 Similarly,::

   159 

   160     ylabel("f(x)")

   161 

   162 sets the name of y-axis as "f(x)"

   163 

   164 {{{ Show the plot window and point to ylabel and switch back to terminal }}}

   165 

   166 {{{ Pause here and try out the following exercises }}}

   167 

   168 %% 5 %% Set the x and y labels as "x" and "f(x)" in LaTex style.

   169 

   170 {{{ continue from paused state }}}

   171 

   172 Since we need LaTex style formatting, all we have to do is enclose the string

   173 in between two $. Hence,::

   174 

   175     xlabel("$x$")

   176     yalbel("$f(x)$")

   177 

   178 does the job for us.

   179 

   180 {{{ Show the plot window with clean labels }}}

   181 

   182 The plot is now almost complete. Except that we have still not seen how to 

   183 name the points. For example the point (2, -1) is the local maxima. We would

   184 like to name the point accordingly. We can do this by using::

   185 

   186     annotate("local maxima", xy=(2, -1))

   187 

   188 {{{ Show the annotation that has appeared on the plot }}}

   189 As you can see, the first argument to =annotate= command is the name we would

   190 like to mark the point as and the argument after xy= is the point at which the

   191 name should appear.

   192 

   193 {{{ Pause here and try out the following exercises }}}

   194 

   195 %% 6 %% Make an annotation called "root" at the point (-4, 0)

   196         What happens to the first annotation ?

   197 

   198 {{{ continue from paused state }}}

   199 

   200 As we can see, every annotate command makes a new annotation on the figure.

   201 

   202 {{{ Show summary slide }}}

   203 

   204 we have looked at 

   205 

   206  * Modifying the attributes of plot by passing additional arguments

   207  * How to add title

   208  * How to incorporate LaTex style formatting

   209  * How to label x and y axes

   210  * How to add annotations

   211 

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

   213 

   214 #[Nishanth]: Will add this line after all of us fix on one.

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

   216 

   217 Hope you have enjoyed and found it useful.

   218 Thankyou

   219  

   220 .. Author              : Nishanth

   221    Internal Reviewer 1 : 

   222    Internal Reviewer 2 : 

   223    External Reviewer   :