I have a large matrix where I want to assign the same value(s) to many matrix elements. Is there a more efficient way to do this rather than iterating over each column and row using for loops? Here is a MWE:
import numpy as np
a = 0.5
b = 0.6
M = np.zeros((16,16)) # empty matrix
np.fill_diagonal(M, 0.9) # diagonal elements
for jj in range(0,16): # rows
for kk in range(0,16): # columns
if jj == 0:
if (kk == 1) | (kk == 3):
M[jj,kk] = a
if jj == 3:
if (kk == 0) | (kk == 2):
M[jj,kk] = b
if jj == 5:
if (kk == 4) | (kk == 6):
M[jj,kk] = a
# etc
print(M)
Answer
A possible solution:
idxr_a = [0, 0, 5, 5] # row index
idxc_a = [1, 3, 4, 6] # col index
M[idxr_a, idxc_a] = a
idxr_b = [3, 3] # row index
idxc_b = [0, 2] # col index
M[idxr_b, idxc_b] = b