Clash Royale CLAN TAG#URR8PPP

counting surrounding true's in numpy matrix (python)

I want to make something similiar to minesweeper

input matrix:

matrix = [[true, false, false],
[false, true, false],
[false, false, false]]


if a bomb is on the field I do not count it as bomb is surrounding.

I thought about doing it with numpy convolve somehow but I am struggling with how to go through the matrix and always check the left, top, right and bottom fields of the actual field (in the case of a border I check "empty" fields which is 0 for sure)

3 Answers
3

Here is a solution using scipy.signal.convolve2d :

scipy.signal.convolve2d

import scipy
import numpy as np

# Input matrix, can be left as boolean
matrix = np.array([[True, False, False],
[False, True, False],
[False, False, False]])

# Our dougnut filter
W = np.array([[1, 1, 1],
[1, 0, 1],
[1, 1, 1]])

# Single convolve
res = convolve2d(matrix, W, 'same')


We get the exact result:

res
array([[1, 2, 1],
[2, 1, 1],
[1, 1, 1]])


boundary

mode

convolve2d

using only numpy, including nd_window from here

numpy

nd_window

m_pad = np.pad(matrix, ((1,1),(1,1)), 'constant', constant_values=(False, False))
filter = np.array([[1,1,1],[1,0,1],[1,1,1]], dtype = bool)
adj_matrix = np.einsum('ijkl,kl->ij', nd_window(m_pad, 3), filter)


Also, you can use scipy.signal.convolve2d

scipy.signal.convolve2d

adj_matrix = convolve2d(matrix, filter, 'same', fillvalue = False)


To keep it simple : using numpy you can simply use the sum() method (https://docs.scipy.org/doc/numpy-1.13.0/reference/generated/numpy.matrix.sum.html).

numpy

sum()

np.matrix(matrix).sum() will count all the True in your matrix.

np.matrix(matrix).sum()

True

So np.matrix(matrix).sum() - matrix[1][1] should return the number of mine around a cell.

np.matrix(matrix).sum() - matrix[1][1]

And for me the easiest way to remove the border problem is to complete your matrix with False cells all around it.

False

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.