Python-3.4.3/C2/Multiple-plots/English-timed
From Script | Spoken-Tutorial
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| 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. |
