[FIXED] Compute the dot product of all combinations of two rows in a matrix

Issue

I'm super new to programming and I'm trying to compute the dot product of all of the combinations of any tow rows in a N*3 matrix.

For example for N = 5 I have matrix

   [0.64363829, 0.21027068, 0.7358777 ],
   [0.39138384, 0.49072791, 0.7784631 ],
   [0.22952251, 0.90537974, 0.35722115],
   [0.40108871, 0.88992243, 0.21717715],
   [0.06710475, 0.84022499, 0.53806962]

and I'd like to compute the dot products of all combinations of the rows like: row1*row2, row1*row3, row1*row4, row1*row5, row2*row3 ... row4*row5.

I'm not sure how to approach this problem so I've tried a few things. So far I have

for i in range(N-1): 
    for l in range(1, N): 
        dotms = (np.dot(nmag[(i),:], nmag[(i+l),:]))
        print(dotms)

where nmag is the 5*3 matrix

the output only has 7 answers, but with 5 rows I'm looking for 10 different combinations

[0.9279489, 0.6009753, 0.6050964, 0.615819, 0.8122099, 0.7627538, 0.8574529]

Thank you in advance for your help!

Solution

Your loop indices don't quite fit for your task:

import numpy as np
nmag = np.array([[0.64363829, 0.21027068, 0.7358777 ],
                 [0.39138384, 0.49072791, 0.7784631 ],
                 [0.22952251, 0.90537974, 0.35722115], 
                 [0.40108871, 0.88992243, 0.21717715],
                 [0.06710475, 0.84022499, 0.53806962]])

for i in range(N-1):  # iterate over all rows but the last
    for j in range(i+1, N):   # start j from i+1 
        dotms = np.dot(nmag[i, :], nmag[j, :])
        print(dotms)

Answered By - scleronomic