Question

How can I efficiently manipulate the elements of a sparse matrix?

Answer 1

You can use methods like getrow(), getcol(), and tolil() to efficiently manipulate sparse matrices.

Example Code: Extracting a Row and Converting to LIL Format

from scipy.sparse import csr_matrix, lil_matrix

# Create a sparse matrix
A = csr_matrix([[1, 0, 2],
                [0, 0, 3],
                [4, 0, 5]])

# Extract the second row as a sparse matrix
row = A.getrow(1)
print(row.toarray())

# Convert the sparse matrix to LIL format
A_lil = A.tolil()
A_lil[1, 1] = 6  # Modify a single element
print(A_lil.toarray())