Python-3.4.3/C2/Multiple-plots/English-timed

Time	Narration
00:01	Hello friends! Welcome to the spoken tutorial on "Multiple plots".
00:07	At the end of this tutorial, you will be able to: draw multiple plots which are overlaid,
00:15	use the figure command,
00:17	use the legend command,
00:20	switch between the plots and perform some operations on each of them like saving the plots.
00:28	To record this tutorial, I am using: Ubuntu Linux 14.04 operating system,
00:36	Python 3.4.3, IPython 5.1.0
00:42	To practise this tutorial, you should know how to: use plots interactively,
00:49	embellish a plot, save plots.
00:53	If not, see the pre-requisite Python tutorials on this website.
00:59	Let us first open the Terminal by pressing Ctrl+Alt+T keys simultaneously.
01:07	Now, type ipython3 and press Enter.
01:13	Let us initialise the pylab package. Type percentage pylab and press Enter.
01:21	Let us create a set of points for our plot by using the command 'linspace'.
01:29	Type x equals to linspace inside the brackets 0 comma 50 comma 10.
01:39	Now, let us draw a simple sine curve using these points. Type plot inside the brackets x comma sin(x).
01:51	As we can see, this sine curve is not a smooth curve. What really caused this?
01:59	This happened because we selected few points that is 10, for this large interval of 0 to 50.
02:08	'Plot' function does not plot the analytical function.
02:12	It plots the points given by the analytical function.
02:17	Now, let us use linspace command to get 500 points between 0 and 50 and draw the sine curve again.
02:29	Type y equals to linspace inside the brackets 0 comma 50 comma 500.
02:39	plot inside the brackets y comma sin(y).
02:45	Now we see a sine curve with a smooth curve.
02:50	Notice, we will also have two plots one overlaid upon another.
02:56	In pylab, by default, all the plots are overlaid.
03:01	To distinguish between two overlaid plots we use the 'legend' command.
03:07	Type legend inside the brackets square brackets sin(x) comma sin(y).
03:16	The legend command takes parameter as a list of strings.
03:21	Then it assigns strings to plots in the order they were created.
03:27	Now, we can see the legends being displayed for the two sine curves on the plot area.
03:34	In the IPython terminal, now type clf() to clear the plot window.
03:41	Pause the video. Try this exercise and then resume the video.
03:46	Draw two plots, first plot being a parabola of the form y equals to 4x square,
03:56	and the second being a straight line of the form y equals to 2x plus 3 in the interval minus 5 to 5.
04:05	Use legends to indicate what each plot is doing.
04:11	Switch to the terminal for solution. Type: x is equal to linspace inside the brackets minus 5 comma 5 comma 100.
04:25	We can obtain the two plots in different colours using the following commands.
04:31	plot inside the brackets x comma 4 multiplied by inside the brackets x multiplied by x.
04:42	plot inside the brackets x comma 2 multiplied by x plus 3.
04:50	Now, we will add a legend to identify the plots.
04:55	Type: legend inside the brackets inside square brackets r inside inverted commas dollar y is equal to 4 x square dollar comma r inside inverted commas dollar y equals to 2x plus 3 dollar.
05:19	We can see the legend added to the plot.
05:24	Next we will learn to switch between the plots and perform operations such as saving the plots etc.
05:33	Let us see how to accomplish this. But, before we move on, let us clear our screen. Type: clf()
05:43	Type: x equals to linspace inside the brackets 0 comma 50 comma 500.
05:53	To accomplish more control over individual plots, we use the 'figure' command. Type: figure(1)
06:03	plot inside the brackets x comma sin(x) comma inside inverted commas b.
06:12	figure(2)
06:14	plot inside the brackets x comma cos(x) comma inside inverted commas g.
06:24	Now, we have two plots, a sine curve and a cosine curve, in two different figures.
06:33	The figure command takes an integer as an argument. This is the serial number of the plot to select corresponding plot.
06:43	All the plot commands we run hereafter are applied to the selected plot. In this example, figure 1 is the sine plot and figure 2 is the cosine plot.
06:56	For example, we can save each plot separately.
07:01	Type: title inside brackets inside inverted commas cos(x).
07:09	savefig inside the brackets inside inverted commas cosine.png
07:18	figure(1)
07:21	title inside the brackets inside inverted commas sin(x).
07:28	savefig inside the brackets inside inverted commas sine.png
07:36	The figures will be saved in current working directory. Now, close both the plot windows.
07:44	Pause the video. Try this exercise and then resume the video.
07:49	Draw a line of the form y equals to x as one figure and another line of the form y is equal to 2x plus 3. Save each of them.
08:05	Switch to the terminal for solution. To solve this problem, we will use the figure command to create first plotting area.
08:15	Type: figure(1) x equals to linspace inside the brackets minus 5 comma 5 comma 100.
08:29	plot inside the brackets x comma x.
08:35	Now, use the figure command to create second plotting area and plot the figure.
08:43	Type: figure(2) plot inside the brackets x comma 2x plus 3.
08:56	We will save the figure as follows.
08:59	Type: figure(1) savefig inside brackets inside inverted commas plot1.png
09:11	figure(2) savefig inside the brackets inside inverted commas plot2.png
09:23	This brings us to the end of this tutorial. In this tutorial, we have learnt to: draw multiple plots which are overlaid,
09:33	use the figure command,
09:35	use the legend command,
09:38	switch between the plots and perform some operations on each of them like saving the plots.
09:46	Here are some self assessment questions for you to solve- What command is used to get individual plots separately?
09:55	What will be the command to identify sine and cosine curve?
10:00	And the answers are- The command "figure()" can get us the individual plots separately.
10:07	The legend command- legend inside the brackets inside square brackets inside inverted commas sin(x) comma inside inverted commas cos(x).
10:21	Please post your timed queries in this forum.
10:26	Please post your general queries on Python in this forum.
10:31	FOSSEE team coordinates the TBC project.
10:35	Spoken-tutorial is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.
10:45	This is Usha from IIT Bombay, signing off. Thank You.

Contributors and Content Editors

PoojaMoolya, Sandhya.np14