Line plot with arrows in matplotlib for all 4 lines plotted with lists of 4 elements-CodePudding

These variables are all lists containing 4 elements. I am trying to get the arrows to show in between these 4 elements for all the lists below in the line plot. In another words, I will have 3 arrows for each of the 4 lines in the plot shown below.

I came across this post that suggested the use of quiver but I am not sure how to apply it to my use case

CodePudding user response：

import numpy as np
import matplotlib.pyplot as plt


median_a, median_b, median_c, median_d = [np.random.random((4, 1)) for _ in range(4)]
median1, median2, median3, median4 = [np.random.random((4, 1)) for _ in range(4)]

x1 = median_a
x2 = median_b
x3 = median_c
x4 = median_d


y1 = median1
y2 = median2
y3 = median3
y4 = median4

deltaX1, deltaX2, deltaX3, deltaX4 = [x[1:]-x[:-1] for x in [x1, x2, x3, x4]]
deltaY1, deltaY2, deltaY3, deltaY4 = [y[1:]-y[:-1] for y in [y1, y2, y3, y4]]



line1 = plt.plot(x1, y1,'bo-',label='B0') 
line2 = plt.plot(x2, y2,'go-',label='B1') 
line3 = plt.plot(x3, y3,'ko-',label='B2')
line4 = plt.plot(x4, y4,'ro-',label='B3') 

arrows1 = plt.quiver(x1[:-1], y1[:-1], deltaX1, deltaY1, scale_units='xy', angles='xy', scale=1)
arrows2 = plt.quiver(x2[:-1], y2[:-1], deltaX2, deltaY2, scale_units='xy', angles='xy', scale=1)
arrows3 = plt.quiver(x3[:-1], y3[:-1], deltaX3, deltaY3, scale_units='xy', angles='xy', scale=1)
arrows4 = plt.quiver(x4[:-1], y4[:-1], deltaX4, deltaY4, scale_units='xy', angles='xy', scale=1)

plt.title("Flow")
plt.ylabel("Speed")
plt.xlabel("Size")


plt.legend()

plt.show()

CodePudding user response：

To prevent the double plotting in the other answers, you can specify the arrow colour directly. Also, since you are plotting four times it would be easier to do it in a loop.

xx = [median_a, median_b, median_c, median_d]
yy = [median1, median2, median3, median4]
colors = ['b', 'g', 'k', 'r']

for idx, (x, y) in enumerate(zip(xx, yy)):
    Q = plt.quiver(x[:-1], y[:-1], x[1:]-x[:-1], y[1:]-y[:-1], color=colors[idx], scale_units='xy', angles='xy', scale=1)
    plt.quiverkey(Q, 0.95, 1-idx/10, 0.05, label=f'B{idx}', labelpos='N')

plt.title("Flow")
plt.ylabel("Speed")
plt.xlabel("Size")

plt.show()