Python-3.4.3/C2/Embellishing-a-plot/English-timed

Time	Narration
00:01	Hello friends! Welcome to the tutorial on "Embellishing a Plot".
00:06	At the end of this tutorial, we will learn to- modify the attributes of the plot -color, line style, linewidth,
00:16	add a title to the plot with embedded LaTeX,
00:20	label x and y axes, add annotations to the plot,
00:26	set and get the limits of axes.
00:30	To record this tutorial, I am using: Ubuntu Linux 14.04 operating system,
00:37	Python 3.4.3, IPython 5.1.0
00:43	To practice this tutorial, you should know how to run basic Python commands on the ipython console and use the Plots interactively.
00:54	If not, see the pre-requisite Python tutorials on this website.
00:59	Let us start ipython3. Open the terminal.
01:05	Type ipython3 and press Enter.
01:11	Let us initialise the pylab package.
01:15	Type: percentage pylab and press Enter.
01:21	We shall first make a simple plot and start modifying it.
01:26	Type: x = linspace inside the brackets minus 2 comma 4 comma 20 and press Enter.
01:40	Then type plot inside the brackets x comma sin(x) and press Enter.
01:49	We can now see the sine curve in the plot window.
01:53	The default colour and thickness of the line is as decided by pylab.
01:59	Let us now change the parameters of this curve.
02:03	We can pass additional arguments to the plot command to do this.
02:09	We shall first clear the plot window by typing clf() in the ipython console.
02:16	You can now see a blank plot window.
02:20	Now, plot the same sine curve with an additional color argument.
02:26	So, we will type plot inside the brackets x comma sin(x) comma inside inverted commas r and press Enter. Here, the argument 'r' is for red color.
02:44	On the plot window, the same sine curve is now seen in red color.
02:50	Do not close the plot window, just minimize it.
02:54	We can alter the thickness of the line by using the 'linewidth' argument.
03:00	This time we will draw the cosine curve on the plot window.
03:05	So, type plot inside brackets x comma cos(x) comma linewidth is equal to 2 and press Enter.
03:18	A cosine curve with line thickness 2 is produced in the plot window.
03:24	Let us now try to plot a sine curve in blue color with linewidth as 3.
03:31	Here onwards, press the Enter key to execute every command that we type on the Ipython console.
03:39	Let us first clear the plot window by typing clf().
03:44	You will again see a blank plot window.
03:48	Now type plot inside the brackets x comma sin(x) comma inside inverted commas b comma linewidth is equal to 3.
04:03	A combination of color and linewidth would do the job for us.
04:08	To get the plot in dotted style instead of a solid style, put a dot in linestyle.
04:16	First, type clf() to clear the plot window.
04:20	Now type plot inside the brackets x comma sin(x) comma inside inverted commas dot.
04:32	We get the sine curve in dotted style.
04:36	Let's see the information of plot.
04:40	Type: plot question mark and press Enter.
04:47	Pause the video. Try this exercise and then resume the video .
04:52	Plot the curve of x verses cos(x) in red dash line and linewidth 3.
05:00	Let us switch to the console for the solution.
05:04	Type clf() to clear the plot window.
05:08	Now type plot inside the brackets x comma cos(x) comma inside inverted commas r hyphen hyphen comma linewidth equals to 3.
05:25	We use a combination of linewidth argument and linestyle.
05:30	Now we know how to produce a bare minimum plot with color, style and thickness.
05:38	Let us look at modifying the plot further.
05:42	Let us start with a plot for the function minus x square plus 4x minus 5.
05:51	Now type plot inside the brackets x comma minus x multiplied by x plus 4 multiplied by x minus 5 comma inside inverted commas r comma linewidth is equal to 2.
06:16	We will see the curve of this equation in the plot window.
06:21	But the figure does not have any description describing the plot.
06:26	To add a title to the plot, use the title command.
06:31	So, type title inside the brackets inside inverted commas Parabolic function minus x square plus 4x minus 5.
06:48	The title command, as you can see, takes a string as an argument.
06:54	We can see the title on the plot window. But it is not formatted and does not look clean.
07:03	It would look even more shabby if there were fractions and complex functions.
07:09	Let us write the title in LaTeX format for a neater look.
07:14	For LaTeX format, we put a dollar sign before and after the string.
07:20	Type title inside the brackets r inside inverted commas Parabolic function dollar minus x square plus 4x minus 5 dollar.
07:38	Here, 'r' means that the string is to be treated as a raw string.
07:45	It will ignore all escape codes.
07:49	As we can see that the polynomial in the title is now formatted.
07:55	Although we have title, the plot is not complete without labelling the x and y axes.
08:03	So, we will label x and y axes in LaTeX style.
08:09	Type xlabel inside the brackets r inside inverted commas dollar x dollar and ylabel inside brackets r inside inverted commas dollar y dollar .
08:30	The plot is now almost complete.
08:34	Now we will name the points considering point(2 comma minus 1) as local maxima.
08:42	To name a point, we use the function annotate.
08:46	Type annotate inside the brackets inside inverted commas local maxima comma xy equals to inside brackets 2 comma minus 1.
09:03	We can see the local maxima at point 2 comma minus 1.
09:09	The first argument in annotate command is the name of the point.
09:15	The second argument represents the coordinates of the point.
09:20	It is a tuple containing two numbers. The first is x coordinate and second is y coordinate.
09:29	Next, type xlim brackets xlim function returns the current x axis limits.
09:39	Then type ylim brackets. ylim function returns the current y-axis limits.
09:49	Set the limits of x-axis from minus 4 to 5 by typing xlim inside the brackets minus 4 comma 5.
10:02	Similarly, set the limits of y-axis in a similar manner.
10:07	Type ylim inside the brackets minus 15 comma 2.
10:19	Pause the video. Try this exercise and then resume the video.
10:24	Make an annotation called "root" at the point (minus 4 comma 0).
10:31	What happens to the first annotation?
10:35	Switch to the Ipython console for the solution.
10:39	Type annotate inside the brackets inside inverted commas root comma xy is equal to minus 4 comma 0.
10:53	Every annotate command makes a new annotation on the figure.
10:59	This brings us to the end of this tutorial. In this tutorial, we have learnt to: modify the attributes of a plot like color, line width, line style by passing additional arguments,
11:16	add title to a plot using 'title command,
11:20	incorporate LaTeX style formatting by adding a $ sign before and after the string,
11:28	label x and y axes using xlabel() and ylabel() commands,
11:34	add annotations to a plot using annotate() command,
11:39	get and set the limits of axes using xlim() and ylim() commands.
11:46	Here are some self assessment questions for you to solve.
11:51	Draw a plot of cosine graph between minus 2pi to 2pi with line thickness 4.
12:00	Read the documentation and find out, is there a way to modify the alignment of text in the command ylabel.
12:09	And the answers are- In order to plot a cosine graph between the points minus 2pi and 2pi with line thickness 4, we use the linspace and plot command as- x equals to linspace inside the brackets minus 2pi comma 2pi.
12:31	plot (x comma cos(x) comma linewidth equals to 4)
12:38	The answer to the second question is: No. We do not have an option to modify the alignment of text in the command ylabel.
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13:34	This is Usha from IIT Bombay, signing off. Thanks for watching.

Contributors and Content Editors

PoojaMoolya, Sandhya.np14