Python: Two Concenctric Circles - check if inside-CodePudding

Let's say I have a system of two concenctric circles and a numpy array with some coordinates. I now want to check if the coordinates are inside the ring and if so I want to print the respective values for example [6, 0], yes? How can I do this? This is what I have done so far but this leads to the following error: TypeError: only size-1 arrays can be converted to Python scalars

import math

import numpy as np

positions = np.array([[2.5, 8], [3, 10], [0, 5], [6, 0]])

x1 = positions[:, 0]

y1 = positions[:, 1]


# Function to check if array coordinate

# lies in the ring

def checkcircle(r, R, r1, x1, y1):

    dis = int(math.sqrt(x1 * x1   y1 * y1))

    return (dis-r1 >= R and dis r1 <= r)

r = 8; R = 4; r1 = 2;

if (checkcircle(r, R, r1, x1, y1)):

    print([{x1}, {y1}]," yes")

  
else:

    print("no")

CodePudding user response：

Your solution was going in the right direction till you passed the points as scalars and they were actually 2D numpy arrays. I have rewritten your code with some modifications and clarifications as to what does what.

import math

import numpy as np

# points to check
positions = np.array([[2.5, 8], [3, 10], [0, 5], [6, 0],[2,1]])


# Function to check if points lies in the ring

def checkcircle(r, R, positions):
    #initialize list to store points that lie in the ring
    points_in_ring = []
    # Go through every point and check its distance from center assuming, the center lies at (0,0) and can be changed later on
    for i in range(positions.shape[0]):
        # Calculate euclidean distance between two points
        dis = math.dist(positions[i],[0.,0.])
        # Print distance for more clarity
        print(dis)
        # If distance is more than inner radius and less than outer radius, store that point in the list
        if dis > R and dis <r:
            points_in_ring.append(positions[i])
    
    return points_in_ring

    
r = 8; R = 4;

checkcircle(r,R, positions)

The math.dist() method returns the Euclidean distance between two points (p and q), where p and q are the coordinates of that point.

Note: The two points (p and q) must be of the same dimensions.

output:

8.381527307120106
10.44030650891055
5.0
6.0
2.23606797749979
[array([0., 5.]), array([6., 0.])]