Fill area between two vectors in matlibplot

Question

The following code calculates the following vectors: the orientation Vector (red) and two vectors (blues) which result by rotating the red vector 60 degree clock -und counterclockwise.

import matplotlib.pyplot as plt
import numpy as np


def Visualize(orienVector,vector1,vector2):
 # Create figure and subplot
 fig = plt.figure()
 ax = fig.add_subplot(1, 1, 1)

 # Plot data points
 #ax.scatter(vector1[0], vector1[1], color='blue')
 #ax.scatter(vector2[0], vector2[1], color='orange')

 # Set limits for x and y axes
 plt.xlim(-1, 1)
 plt.ylim(-1, 1)

 # ===== Important bits start here =====

 # Set properties of spines
 ax.spines['top'].set_color('none')
 ax.spines['left'].set_position('zero')
 ax.spines['right'].set_color('none')
 ax.spines['bottom'].set_position('zero')

 # Set axis tick positions
 ax.xaxis.set_ticks_position('bottom')
 ax.yaxis.set_ticks_position('left')

 # Set specific tick locations
 ax.set_xticks([-10,-5, 0, 5 , 10])
 ax.set_yticks([-10,-5, 0, 5 , 10])

 # ===== End Of Important Bits =====

 # Draw arrows
 ax.arrow(0, 0 , vector1[0][0], vector1[1][0], 
    head_width=0.03, 
    head_length=0.1, 
    lw=1, 
    fc='blue', 
    ec='blue', 
    length_includes_head=True)
    
 ax.arrow(0, 0 , vector2[0][0], vector2[1][0], 
    head_width=0.03, 
    head_length=0.1, 
    lw=1, 
    fc='blue', 
    ec='blue', 
    length_includes_head=True)

 ax.arrow(0, 0 , orienVector[0][0], orienVector[1][0], 
    head_width=0.03, 
    head_length=0.1, 
    lw=2, 
    fc='red', 
    ec='red', 
    length_includes_head=True)

 plt.show()

# rotation matrix clockwise
def rotMatrixClockWise(angle):
 c, s = np.cos(angle), np.sin(angle)
 R = np.array([[c, -s], [s, c]])
 return R 

# rotation matrix clockwise
def rotMatrixCounterClockWise(angle):
 c, s = np.cos(angle), np.sin(angle)
 R = np.array([[c, s], [-s, c]])
 return R  

# center of the poit of interests POIS
POI_X = [10,12,15,17,20,50]
POI_Y = [20,30,25,22,19,35]

# position of the pedestrian 
pedPostion = np.array([[3],[4]])

# range of the horisontal angel view
spanningAngle = np.radians(60)

# calculate the cone 
for angle in range(0,360,5):
 
    
 # calculating the component of orientation vector V0, where the length |V0| = 1 
 x0 = 5*np.cos(np.radians(angle))
 y0 = 5*np.sin(np.radians(angle)) 
 v0 = np.array([[x0],[y0]])
 
 v1 = rotMatrixCounterClockWise(spanningAngle).dot(v0) 
 v2 = rotMatrixClockWise(spanningAngle).dot(v0) 


 Visualize(v0,v1,v2)

The output of this vector looks like

output

I'm trying to fill the area between the blue vectors to obtain a cone like the following:

concept Output

The distance between the head of the cone (0,0) and the arc is always 5

However, I can't get it to work. I'm new to Matlibplot

user_6843348 · Answer

You could figure out analytically the points in the arc (a portion of a circle, so y = +- (1-x^2)**0.5), add them to the polygon defined by the origin and extremities of red and yellow vectors, then use https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.fill.html.

An example of filling a polygon is here: https://matplotlib.org/stable/gallery/lines_bars_and_markers/fill.html#sphx-glr-gallery-lines-bars-and-markers-fill-py

user_7343721 · Answer

Maybe not completely what you are looking for, but you could create a wedge between the vectors. It would be more appropriate to fit an ellipse and fill the coordinates in between. Here is an example for the wedge.

import matplotlib.pyplot as plt, numpy as np
from matplotlib import patches
v1 = np.array((1, 2))
v2 = np.array((1, -2))
base = np.array((0, 0))
theta1 = np.rad2deg(np.arctan(v1[1] / v1[0]))
theta2 = np.rad2deg(np.arctan(v2[1] / v2[0]))

fig, ax = plt.subplots()

a, b = theta1, theta2 
if b > a:
   a, b = b, a
artist = patches.Arc(base, 
            width = 1,
            height = 1, 
            theta1 = a, 
            theta2 = b,
            color = 'green')
ax.arrow(*base,  *v1, color = 'black')
ax.arrow(*base,  *v2, color = 'black')
ax.arrow(*base, *(v2 + v1), color = 'red')
wedge = patches.Wedge(base, 
            r = 1,
            width = 1, 
            theta1 = theta2, 
            theta2 = theta1,
            color = 'green')
ax.add_patch(wedge)

fig.show()

Fill area between two vectors in matlibplot

2 Answers