--- a/embellishing_a_plot.rst Thu Oct 07 14:21:53 2010 +0530
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,446 +0,0 @@
-.. Author : Nishanth
- Internal Reviewer 1 : Anoop
- Internal Reviewer 2 : Madhu
- External Reviewer :
-
-.. Prerequisites: using ``plot`` command
-
-Hello friends and welcome to the tutorial on Embellishing Plots.
-
-{{{ Show the slide containing title }}}
-
-{{{ Show the slide containing the outline }}}
-
-In this tutorial, we shall look at how to modify the colour, thickness and
-linestyle of the plot. We shall then learn how to add title to the plot and
-then look at adding labels to x and y axes. we shall also look at adding
-annotations to the plot and setting the limits of axes.
-
-Let us start ipython with pylab loaded, by typing on the terminal
-
-{{{ shift to terminal and type ipython -pylab }}}
-
-::
-
- ipython -pylab
-
-.. #[madhu: I feel the instructions should precede the actual action,
-
-since while recording we need to know before hand what we need to do]
-
-We shall first make a simple plot and start decorating it.
-
-.. #[madhu: start decorating it should be fine, with is not necessary]
-
-::
-
- x = linspace(-2, 4, 20)
- plot(x, sin(x))
-
-.. #[madhu: Standard is to choose between -50 to 50 or 0 to 50 with 100
- points right?]
-
-As we can see, the default colour and the default thickness of the
-line is as decided by pylab. Wouldn't be nice if we could control
-these parameters in the plot? This is possible by passing additional
-arguments to the plot command.
-
-.. #[[Anoop: I think it will be good to rephrase the sentence]]
-.. #[madhu: Why "you" here? Shouldn't this be "we" as decided? Also I
- added "the default" check the diff]
-
-The additional argument that we shall be passing in here now is the
-colour argument. We shall first clear the figure and plot the same in
-red colour. Hence
-
-.. #[Madhu: Note the diff for changes]
- ::
-
- clf()
- plot(x, sin(x), 'r')
-
-As we can see we have the same plot but now in red colour.
-
-.. #[Madhu: diff again]
-
-To alter the thickness of the line, we use the ``linewidth`` argument in the plot
-command. Hence
-::
-
- plot(x, cos(x), linewidth=2)
-
-produces a plot with a thicker line, to be more precise plot with line
-thickness 2.
-
-.. #[[Anoop: I guess it will be good if you say that it affects the
- same plot, as you have not cleared the figure]]
-.. #[Madhu: To Anoop, not necessary I feel since they can see it?]
-
-{{{ Show the plot and compare the sine and cos plots }}}
-
-{{{ Pause here and try out the following exercises }}}
-
-.. #[[Anoop: is the above a context switch for the person who does the
- recording, other wise if it an instruction to the person viewing
- the video, then I guess the three braces can be removed.]]
-
-%% 1 %% Plot sin(x) in blue colour and with linewidth as 3
-
-{{{ continue from paused state }}}
-
-A combination of colour and linewidth would do the job for us. Hence
-::
-
- clf()
- plot(x, sin(x), 'b', linewidth=3)
-
-.. #[[Anoop: add clf()]]
-
-produces the required plot
-
-.. #[Nishanth]: I could not think of a SIMPLE recipe approach for
- introducing linestyle. Hence the naive approach.
-
-.. #[[Anoop: I guess the recipe is fine, but would be better if you
- add the problem statement rather than just saying "let's do a simple
- plot"]]
-
-.. #[Madhu: It is good enough.]
-
-Occasionally we would also want to alter the style of line. Sometimes
-all we want is just a bunch of points not joined. This is possible by
-passing the linestyle argument along with or instead of the colour
-argument. Hence ::
-
- clf()
- plot(x, sin(x), '.')
-
-produces a plot with only points.
-
-To produce the same plot but now in blue colour, we do
-::
-
- clf()
- plot(x, sin(x), 'b.')
-
-Other available options can be seen in the documentation of plot.
-::
-
- plot?
-
-{{{ Run through the documentation and show the options available }}}
-
-{{{ Show the options available for line style and colors }}}
-
-.. #[Madhu: The script needs to tell what needs to be shown or
- explained.]
-
-{{{ Pause here and try out the following exercises }}}
-
-.. #[[Anoop: same question as above, should it be read out?]]
-
-%% 2 %% Plot the sine curve with green filled circles.
-
-{{{ continue from paused state }}}
-
-All we have to do is use a combination of linestyle and colour to acheive this.
-Hence
-::
-
- clf()
- plot(x, cos(x), 'go')
-
-produces the required plot.
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 3 %% Plot the curve of x vs tan(x) in red dashed line and linewidth 3
-
-{{{ continue from paused state }}}
-
-.. #[Madhu: I did not understand the question]
-
-Now that we know how to produce a bare minimum plot with colour, style
-and thickness of our interest, we shall look at decorating the plot.
-
-Let us start with a plot of the function -x^2 + 4x - 5.
-::
-
- plot(x, -x*x + 4*x - 5, 'r', linewidth=2)
-
-{{{ Show the plot window and switch back to terminal }}}
-
-We now have the plot in a colour and linewidth of our interest. As you can see,
-the figure does not have any description describing the plot.
-
-.. #[Madhu: Added "not". See the diff]
-
-We will now add a title to the plot by using the ``title`` command.
-::
-
- title("Parabolic function -x^2+4x-5")
-
-{{{ Show the plot window and point to the title }}}
-
-The figure now has a title which describes what the plot is. The
-``title`` command as you can see, takes a string as an argument and sets
-the title accordingly.
-
-.. #[Madhu: See the diff]
-
-The formatting in title is messed and it does not look clean. You can imagine
-what would be the situation if there were fractions and more complex functions
-like log and exp. Wouldn't it be good if there was LaTex like formatting?
-
-That is also possible by adding a $ sign before and after the part of the
-string that should be in LaTex style.
-
-for instance, we can use
-::
-
- title("Parabolic function $-x^2+4x-5$")
-
-and we get the polynomial formatted properly.
-
-.. #[Nishanth]: Unsure if I have to give this exercise since enclosing the whole
- string in LaTex style is not good
-
-.. #[[Anoop: I guess you can go ahead with the LaTex thing, it's
- cool!]]
-.. #[Madhu: Instead of saying LaTeX style you can say Typeset math
- since that is how it is called as. I am not sure as well. It
- doesn't really solve the purpose]
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 4 %% Change the title of the figure such that the whole title is formatted
- in LaTex style
-
-{{{ continue from the paused state }}}
-
-The solution is to enclose the whole string in between $. Hence,
-::
-
- title("$Parabolic function -x^2+4x-5$")
-
-gives a title that looks neatly formatted.
-
-Although we have title, the plot is not complete without labelling x
-and y axes. Hence we shall label x-axis to "x" and y-axis to "f(x)" ::
-
- xlabel("x")
-
-{{{ Switch to plot window and show the xlabel }}}
-
-As you can see, ``xlabel`` command takes a string as an argument,
-similar to the ``title`` command and sets it as the label to x-axis.
-
-.. #[See the diff]
-
-Similarly,
-::
-
- ylabel("f(x)")
-
-sets the name of the y-axis as "f(x)"
-
-{{{ Show the plot window and point to ylabel and switch back to the terminal }}}
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 5 %% Set the x and y labels as "x" and "f(x)" in LaTex style.
-
-{{{ continue from paused state }}}
-
-Since we need LaTex style formatting, all we have to do is enclose the string
-in between two $. Hence,
-::
-
- xlabel("$x$")
- yalbel("$f(x)$")
-
-does the job for us.
-
-{{{ Show the plot window with clean labels }}}
-
-The plot is now almost complete. Except that we have still not seen how to
-name the points. For example the point (2, -1) is the local maxima. We would
-like to name the point accordingly. We can do this by using
-::
-
- annotate("local maxima", xy=(2, -1))
-
-{{{ Show the annotation that has appeared on the plot }}}
-
-As you can see, the first argument to ``annotate`` command is the name we would
-like to mark the point as and the second argument is the co-ordinates of the
-point at which the name should appear. It is a sequence containing two numbers.
-The first is x co-ordinate and second is y co-ordinate.
-
-.. #[[Anoop: I think we should tell explicitely that xy takes a
- sequence or a tuple]]
-.. #[Madhu: Agreed to what anoop says and also that xy= is the point
- part should be rephrased I think.]
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 6 %% Make an annotation called "root" at the point (-4, 0)
- What happens to the first annotation ?
-
-{{{ continue from paused state }}}
-
-As we can see, every annotate command makes a new annotation on the figure.
-
-Now we have everything we need to decorate a plot. but the plot would be
-incomplete if we can not set the limits of axes. This is possible using the
-button on the plot window.
-
-we shall look at how to get and set them from the script.
-::
-
- xlim()
- ylim()
-
-We see that ``xlim`` function returns the current x axis limits and ylim
-function returns the current y-axis limits.
-
-Let us look at how to set the limits.
-::
-
- xlim(-4, 5)
-
-We see the limits of x-axis are now set to -4 and 5.
-Similarly
-::
-
- ylim(-15, 2)
-
-sets the limits of y-axis appropriately.
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 7 %% Set the limits of axes such that the area of interest is the rectangle
- (-1, -15) and (3, 0)
-
-{{{ continue from paused state }}}
-
-As we can see, the lower upper limits of x-axis in the question are -1 and 3.
-The limits of y-axis are -15 and 0.
-
-::
-
- xlim(-1, 3)
- ylim(-15, 0)
-
-Gives us the required rectangle.
-
-{{{ Show summary slide }}}
-
-we have looked at
-
- * Modifying the attributes of plot by passing additional arguments
- * How to add title
- * How to incorporate LaTex style formatting
- * How to label x and y axes
- * How to add annotations
- * How to set the limits of axes
-
-{{{ Show the "sponsored by FOSSEE" slide }}}
-
-.. #[Nishanth]: Will add this line after all of us fix on one.
-
-This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India
-
-Hope you have enjoyed and found it useful.
-Thankyou
-
-Questions
-=========
-
- 1. Draw a plot of cosine graph between -2pi to 2pi with line thickness 4
-
- Answer::
-
- x = linspace(-2*pi, 2*pi)
- plot(x, cos(x), linewidth=4)
-
- 2. Draw a plot of the polynomial x^2-5x+6 in the range 0 to 5 in blue dotted
- line
-
- Answer::
-
- x = linspace(-2*pi, 2*pi)
- plot(x, x**2 - 5*x + 6, 'r.')
-
- 3. Which marker is used to get circles
-
- a. '.'
- #. '^'
- #. 'o'
- #. '--'
-
- 4. What does the '^' marker produce
-
- Answer: Triangle up marker
-
- 5. How do you set the title as x^2-5x+6 in LaTex style formatting
-
- Answer: title("$x^2-5x+6$")
-
-6. What happens when the following code is executed::
-
- xlabel("First label")
- xlabel("Second label")
-
- Answer: The label of x-axis is set to "Second label"
-
- 7. Read thorugh the documentation and find out is there a way to modify the
- alignment of text in the command ``ylabel``
-
- a. Yes
- #. No
-
- Answer: No
-
- 8. How to add the annotation "Maxima" at the point (1, 2)
-
- Answer: annotate("Maxima", xy=(1, 2))
-
- 9. Is the command ``annotate("max", (1, 2))`` same as ``annotate("max",
- xy=(1, 2)``
-
- a. True
- b. False
-
- Answer: True
-
- 10. When a new annotation is made at a point, what happens to the old one
-
- a. It is replaced
- b. It is overwritten
- c. The new annotation is combined with old one
-
- Answer: It is overwritten
-
- 11. What happens when xlim is used without arguments
-
- Answer: It gives the current limits of x-axis
-
- 12. What happens when ``ylim(0, 5)`` is used
-
- Answer: It sets the lower and upper limits of y-axis to 0 and 5
-
- 13. Draw a cosine plot from 0 to 2*pi with green dots. annotate the origin as
- "origin" and set x and y labels to "x" and cos(x) and x limits to 0 and
- 2pi and y limits to -1.2 and 1.2
-
- Answer::
-
- x = linspace(0, 2*pi)
- plot(x, cos(x), 'g.')
- annotate("origin", (0, 0))
- xlabel("$x$")
- ylabel("$cos(x)$")
- xlim(0, 2*pi)
- ylim(-1.2, 1.2)
-