Matplotlib.axes.Axes.quiverkey() in Python

Last Updated : 19 Apr, 2020

Matplotlib is a library in Python and it is numerical - mathematical extension for NumPy library. The Axes Class contains most of the figure elements: Axis, Tick, Line2D, Text, Polygon, etc., and sets the coordinate system. And the instances of Axes supports callbacks through a callbacks attribute.

matplotlib.axes.Axes.quiverkey() Function

The Axes.quiverkey() function in axes module of matplotlib library is also used to add a key to a quiver plot.

Syntax: Axes.quiverkey(self, Q, X, Y, U, label, **kw) Parameters: This method accept the following parameters that are described below:

Q: This parameter is the Quiver instance returned by a call to quiver.

X, Y : These parameter are the x and y coordinates of the location of the key.

U: This parameter is the length of the key.

label: This parameter is a string with the length and units of the key.

angles : This parameter is the angle of the arrows.

color : This parameter is the overrides face and edge colors from Q.

labelpos : This parameter is used to position the label above, below, to the right, to the left of the arrow.

labelsep: This parameter is the distance in inches between the arrow and the label.

labelcolor: This defaults to default Text color.

fontproperties: This parameter is the dictionary with keyword arguments accepted by the FontProperties initializer: family, style, variant, size, weight.

Below examples illustrate the matplotlib.axes.Axes.quiverkey() function in matplotlib.axes: Example 1:

Python3

# Implementation of matplotlib function
import matplotlib.pyplot as plt
import numpy as np
     
X = np.arange(-20, 20, 0.5)
Y = np.arange(-20, 20, 0.5)
U, V = np.meshgrid(X, Y)
 
fig, ax = plt.subplots()
q = ax.quiver(X, Y, U, V)
ax.quiverkey(q, X = 0.5, Y = 0.5, U = 500,
             label ='Quiver key')
 
ax.set_title('matplotlib.axes.Axes.quiverkey() \
Example', fontsize = 14, fontweight ='bold')
plt.show()

Output:

Example 2:

Python3

# Implementation of matplotlib function
import matplotlib.pyplot as plt
import numpy as np
     
X, Y = np.meshgrid(np.arange(0, 2 * np.pi, .2), np.arange(0, 2 * np.pi, .2))
U = np.cos(X**2)
V = np.sin(Y**2)
C = U**2 + V**2
 
fig, ax = plt.subplots()
Q = ax.quiver(X, Y, U, V, C, units ='width')
ax.quiverkey(Q, 0.4, 0.9, 1,
             r'val = $Cos(x ^ 2)^2 + Sin(x ^ 2)^2$',
             labelpos ='E',
             coordinates ='figure')

ax.set_title('matplotlib.axes.Axes.quiverkey() \
Example\n', fontsize = 14, fontweight ='bold')
plt.show()