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pythonnumpymatrixscipysparse-matrix

Scipy sparse matrix multiplication

I have this example of matrix by matrix multiplication using numpy arrays:

import numpy as np
m = np.array([[1,2,3],[4,5,6],[7,8,9]])
c = np.array([0,1,2])
m * c
array([[ 0,  2,  6],
       [ 0,  5, 12],
       [ 0,  8, 18]])

How can i do the same thing if m is scipy sparse CSR matrix? This gives dimension mismatch:

sp.sparse.csr_matrix(m)*sp.sparse.csr_matrix(c)
Solution

  • You can call the multiply method of csr_matrix to do pointwise multiplication. 

    sparse.csr_matrix(m).multiply(sparse.csr_matrix(c)).todense()

# matrix([[ 0,  2,  6],
#         [ 0,  5, 12],
#         [ 0,  8, 18]], dtype=int64)