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Matplotlib - Axis Limits & Scales



Axis Limits

Matplotlib automatically arrives at the minimum and maximum values of variables to be displayed along x, y (and z axis in case of 3D plot) axes of a plot. However, it is possible to set the limits explicitly by using Axes.set_xlim() and Axes.set_ylim() functions.

Syntax

#sets the x-axis view limits
Axes.set_xlim(self, left=None, right=None, 
              auto=False, xmin=None, xmax=None)

#sets the y-axis view limits
Axes.set_ylim(self, bottom=None, top=None, 
              auto=False, ymin=None, ymax=None)

Parameters

left, right Optional. The left and right xlim in data coordinates. Passing None leaves the respective limit unchanged.
xmin, xmax Optional. Equivalent to left and right respectively, and it is an error to pass both xmin and left or xmax and right.
bottom, top Optional. The bottom and top ylim in data coordinates. Passing None leaves the respective limit unchanged.
ymin, ymax Optional. Equivalent to bottom and top respectively, and it is an error to pass both ymin and bottom or ymax and top.
auto Optional. Specify whether to turn on autoscaling of the x-axis / y-axis. True turns on, False turns off (default action), None leaves unchanged.

Example:

In the example below, although the x is defined from 0 to 20, the view limit is set to 0 to 15. Similarly, y has range -1 to 1, the view limit is set to -0.9 to 0.9.

import matplotlib.pyplot as plt
import numpy as np

#creating a array of values between
#0 to 20 with a difference of 0.1
x = np.arange(0, 20, 0.1)
y = np.sin(x)

fig, ax = plt.subplots()

#plotting curves
ax.plot(x, y) 

#formatting axes
ax.set_title("Truncated Sine Wave") 
ax.set_xlabel("x")
ax.set_ylabel("y")
ax.set_xlim(0,15)
ax.set_ylim(-0.9, 0.9)

#displaying the figure
plt.show()

The output of the above code will be:

Axis Limits and Scales

Axis Scales

There are instances when a different scale of x-axis or y-axis is needed. In Matplotlib, it is possible change the scale of the axis using Axes.set_xscale() and Axes.set_yscale() functions.

Syntax

#sets the x-axis scale
Axes.set_xscale(self, value, **kwargs)

#sets the y-axis scale
Axes.set_yscale(self, value, **kwargs)

Parameters

value Optional. Specify axis scale type to apply. It can be chosen from {'linear', 'log', 'symlog', 'logit', ...}.

Example:

In the example below demonstrates how to plot graphs in different scales.

import matplotlib.pyplot as plt
import numpy as np

#creating a array of values between
#0 to 5 with a difference of 0.1
x = np.arange(0, 5, 0.1)
y1 = np.exp(x)
y2 = x**2

fig, (ax1, ax2) = plt.subplots(1,2)

#first plot - normal scale
ax1.plot(x, y1) 
ax1.plot(x, y2)
ax1.set_title("Normal Scale") 
ax1.set_xlabel("x")
ax1.set_ylabel("y") 
ax1.legend(['exp(x)', 'x**2'])

#second plot - log scale
ax2.set_yscale("log")
ax2.plot(x, y1) 
ax2.plot(x, y2) 
ax2.set_title("Log Scale") 
ax2.set_xlabel("x") 
ax2.legend(['exp(x)', 'x**2'])

#displaying the figure
plt.show()

The output of the above code will be:

Axis Limits and Scales

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