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Matplotlib Multiplots with subplots() Function

In this tutorial, we will cover how to draw multiple plots in a single graph in matplotlib.

You must be thinking, why would we want to have multiple plots in a single graph. That will only lead to confusion and clutter. But if you need to either do comparison between the two curves or if you want to show some gradual changes in the plots(relative to each other), etc. in that case multiple plots are useful.

In matplotlib, we can do this using Subplots.

The subplots() function is in the pyplot module of the matplotlib library and is used for creating subplots/multiplots in an effective manner.

subplots() Function

This function will create a figure and a set of subplots. It is basically a wrapper function and which is used to create common layouts of subplots(including the enclosing figure object) in a single call.

  • This function mainly returns a figure and an Axes object or also an array of Axes objects.

  • If you use this function without any parameters then it will return a Figure object and one Axes object.

Syntax of suplots() Function:

Given below is the syntax for using this function:

subplots(nrows, ncols, sharex, sharey, squeeze, subplot_kw, gridspec_kw, **fig_kw)

Parameters:

Let us discuss the parameters used by this function:

  • nrows, ncols

    The parameter nrows is used to indicate the number of rows and the parameter ncols is used to indicate the number of columns of the subplot grid. Both parameters have a default value as 1.

  • sharex, sharey

    To control the sharing of properties among x (sharex) or among y (sharey) axis these parameters are used.

  • squeeze

    This optional parameter usually contains boolean values with the default is True.

  • subplot_kw

    This parameter is used to indicate the dict with keywords that are passed to the add_subplot call which is used to create each subplot.

  • gridspec_kw

    This parameter is used to indicate the dict with keywords passed to the GridSpec constructor that is used to create the grid on which the subplots are placed on.

  • **fig_kw

    All the additional keyword arguments passed to the .pyplot.figure call are part of this parameter.

Now we will cover some examples so that all the concepts become clear for you.

Example1: Plot with one Figure and an Axes

The code for this example is as follows:

import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 2*np.pi, 400)
y = np.sin(x**2) + np.cos(x)

fig, ax = plt.subplots()
ax.plot(x, y)
ax.set_title('Simplest plot in the matplotlib')

Now its time to take a look the output for the code:
creating subplots in Matplotlib

In this we have used the subplots() function, but we haven't added two plots to the graph. So the subplots() function can be normally used to create a single graph/plot as well.

Example 2: Stacked Plots

Let us cover an example for stacked plots. We will try to plot a sequence of plots (i.e 2 here) just by stacking one over the other. As there is the stacking of plots, so the number of rows (i.e nrows) will change, which means ncols stay the same as 1. Also, Each subplot is identified by the index parameter.

The code snippet for this is as follows:

import numpy as np
import matplotlib.pyplot as plt

plt.figure(figsize=(6, 4))

def f(x):
    return np.sin(x) - x * np.cos(x)

def fp(x):
    """ The derivative function of f """
    return x * np.sin(x)

X = np.arange(-5, 5.0, 0.05)

fig, ax = plt.subplots(2, 
           sharex='col', sharey='row')

ax[0].plot(X, f(X), 'bo', X, f(X), 'k')
ax[0].set(title=' function f')

ax[1].plot(X, fp(X), 'go', X, fp(X), 'k')
ax[1].set(xlabel='X Values', ylabel='Y Values',
       title='Derivative Function of f')

plt.show()

Here is the output of the above code:

creating subplots in Matplotlib

As ou can see in the output above that two plots are stacked one on top of the other. The plot can be of some other type too. But when you want to do some comparison between plots, this is a good approach.

Example 3: Plot within another Plot

For this code example. let's take a live example.

You can use the above terminal to run the other examples too and see the output. Try making different plots too.

Summary:

In this tutorial, we covered how to create multiple plots in matplotlib using the subplots() function. We also covered different arrangements for the multiple plots in a single figure.