`numpy.matrixlib.defmatrix:matrix.sum`

Signature

def sum(self, axis = None, dtype = None, out = None)

Returns the sum of the matrix elements, along the given axis.

Refer to numpy.sum for full documentation.

This is the same as ndarray.sum, except that where an ndarray would be returned, a matrix object is returned instead.

x = np.matrix([[1, 2], [4, 3]])

✓

x.sum()

✗

np.int64(10)

x.sum(axis=1)
x.sum(axis=1, dtype='float')
out = np.zeros((2, 1), dtype='float')
x.sum(axis=1, dtype='float', out=np.asmatrix(out))

✓

matrix([[3.],
        [7.]])