Difference between revisions of "Python-3.4.3/C2/Multiple-plots/English"

containing title, name of the production team along with the logo of MHRD

Objectives

1. Draw multiple plots which are overlaid.
2. Use the figure command.
3. Use the legend command.
4. Switch between the plots and perform some operations on each of them like saving the plots.

System Requirements

• Ubuntu Linux 14.04 operating system
• Python 3.4.3
• IPython 5.1.0

Pre-requisites

• use Plots interactively
• Embellish a plot
• Save plots

If not, see the pre-requisite Python tutorials on this website.

ipython3

Now, type ipython3 and press Enter.

%pylab and press Enter.

Type percentage pylab and press Enter.

x = linspace(0, 50, 10)

Type x equals to linspace inside the brackets 0 comma 50 comma 10

plot(x, sin(x))

Type plot inside the brackets x comma sin(x)

Plot function does not plot the analytical function.

It plots the points given by the analytical function.

y = linspace(0, 50, 500)

plot(y, sin(y))

Type

y equals to linspace inside the brackets 0 comma 50 comma 500.

plot inside the brackets y comma sin(y)

Notice we also have two plots one overlaid upon another.

In pylab, by default all the plots are overlaid.

legend(['sin(x)', 'sin(y)'])

Type legend inside the brackets square brackets sin(x) comma sin(y).

The legend command takes parameter as a list of strings.

Then it assigns strings to plots in the order they were created.

Exercise 1

Draw two plots for the given form

1. First plot is a parabola of the form y = 4(x ^ 2)
2. Second plot is a straight line of the form y = 2x + 3 in the interval -5 to 5.
3. Use legends to indicate each plot.

Draw two plots first plot being a parabola of the form y equals to 4x square

and

the second being a straight line of the form y equals to 2x plus 3 in the interval minus 5 to 5.

Use legends to indicate what each plot is doing.

x = linspace(-5, 5, 100)

plot(x, 4 * (x * x))

plot(x, (2 * x) + 3)

Type x equals to linspace inside the brackets minus 5 comma 5 comma 100

We can obtain the two plots in different colours using the following commands.

Type

plot inside the brackets x comma 4 multiplied by inside the brackets x multiplied by x.

plot inside the brackets x comma (2 multiplied by x) plus 3

legend([r'$y = 4(x ^ 2)$', r'$y = 2x + 3$'])

Type legend inside the brackets inside square brackets r inside inverted commas dollar y equals to 4 x square dollar comma r inside inverted commas dollar y equals to 2x plus 3 dollar.

<Pause>

clf()

Let us see how to accomplish this.

But before we move on, let us clear our screen.

Type clf()

x = linspace(0, 50, 500)

Type x equals to linspace inside the brackets 0 comma 50 comma 500

figure(1)

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

figure(2)

plot(x, cos(x), 'g')

To accomplish more control over individual plots we use the figure command

Type

figure(1)

plot inside the brackets x comma sin(x) comma inside inverted commas b

figure(2)

plot inside the brackets x comma cos(x) comma inside inverted commas g

This is the serial number of the plot to select corresponding plot.

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.

title('cos(x)')

savefig('cosine.png')

figure(1)

title('sin(x)')

savefig('sine.png')

Type

title inside brackets inside inverted commas cos(x)

savefig inside brackets inside inverted commas cosine.png

figure(1)

title inside brackets inside inverted commas sin(x)

savefig inside brackets inside inverted commas sine.png

The figures will be saved in current working directory.

Now close both the plot windows.

Exercise2

Draw a line of the form y equals to x as one figure and another line of the form y equals to 2x plus 3.

Save each of them.

figure(1)

x = linspace(-5, 5, 100)

plot(x, x)

To solve this problem we will use the figure command to create first plotting area

Type

figure(1)

x equals to linspace inside the brackets minus 5 comma 5 comma 100

plot inside the brackets x comma x

figure(2)

plot(x, ((2 * x) + 3))

Type

figure(2)

plot inside the brackets x comma 2x plus 3

figure(1)

savefig('plot1.png')

figure(2)

savefig('plot2.png')

We will save the figure as follows.

Type

figure(1)

savefig inside brackets inside inverted commas plot1.png

figure(2)

savefig inside brackets inside inverted commas plot2.png

Summary slide

1. Draw multiple plots which are overlaid.
2. Use the figure command.
3. Use the legend command.
4. Switch between the plots and perform some operations on each of them like saving the plots.

Evaluation

1. What command is used to get individual plots separately?
2. What will be the command to identify sine and cosine curve?

Solutions

1. The command "figure()" can get us the individual plots separately.
2. legend inside brackets inside square brackets inside inverted commas sin(x) comma inside inverted commas cos(x)

Forum

Fossee Forum

Textbook Companion

Acknowledgement

For more details, visit this website.

Thank You

Thank You