Getting Started

Getting Started

After installing Matplotlib, we will begin coding by importing Matplotlib using the command:

import matplotlib.pyplot as plt

Now you have imported Matplotlib in your workspace. You need to display the plots. Using Matplotlib from within a Python script, you have to add plt.show() method inside the file to display your plot.

Example

import matplotlib.pyplot as plt

plt.plot([1,2,3,4])

plt.show()

Output

This window is a matplotlib window, which allows you to see your graph. You can hover the graph and see the coordinates in the bottom right.

You may be wondering why the x-axis ranges from 0-3 and the y-axis from 1-4. If you provide a single list or array to the plot () command, matplotlib assumes it is a sequence of y values, and automatically generates the x values for you. Since python ranges start with 0, the default x vector has the same length as y but starts with 0. Hence the x data are [0, 1, 2, 3].

plot() is a versatile command, and will take an arbitrary number of arguments.

Program

For example, to plot x versus y, you can issue the command:

import matplotlib.pyplot as plt

plt.plot([1,2,3,4], [1,4,9,16])

plt.show()

This .plot takes many parameters, but the first two here are 'x' and 'y' coordinates. This means, you have 4 co-ordinates according to these lists: (1,1), (2,4), (3,9) and (4,16).

Plotting Two Lines

To plot two lines, use the following code:

import matplotlib.pyplot as plt

x = [1,2,3]

y = [5,7,4]

x2 = [1,2,3]

y2 = [10,14,12]

plt.plot(x, y, label='Line 1')

plt.plot(x2, y2, label='Line 2')

plt.xlabel('X-Axis')

plt.ylabel('Y-Axis')

plt.title('LINE GRAPH')

plt.legend()

plt.show()

Output

With plt.xlabel and plt.ylabel, you can assign labels to those respective axis. Next, you can assign the plot's title with plt.title, and then you can invoke the default legend with plt. legend().

Buttons in the output

In the output figure, you can see few buttons at the bottom left corner. Let us see the use of these buttons.

Home Button → The Home Button will help once you have begun navigating your chart. If you ever want to return back to the original view, you can click on this.

Forward/Back buttons → These buttons can be used like the Forward and Back buttons in your browser. You can click these to move back to the previous point you were at, or forward again.

Pan Axis → This cross-looking button allows you to click it, and then click and drag your graph around.

Zoom → The Zoom button lets you click on it, then click and drag a square that you would like to zoom into specifically. Zooming in will require a left click and drag. You can alternatively zoom out with a right click and drag.

Configure Subplots → This button allows you to configure various spacing options with your figure and plot.

Save Figure → This button will allow you to save your figure in various forms.