I have been caught out writing a simple function that manipulates the elements of a matrix.

I have distilled the problem into the code below.

I find that 'sum' works with a Numeric array but fails with a Matrix. Am I doing something wrong? If not, what should I do to patch it?

(I am working under Windows with Numpy 23.0)

Here is the code:

# 'a' is a two dimensional array. The # function simply places the sum of # the first column in a[0,0] def sum(a): N = a.shape[0] sum = 0 for i in range(N): sum += a[i,0]

# This is the criticial line a[0,0] = sum

return a[0,0]

#------------------------ if(__name__ == '__main__'):

import Numeric import Matrix

a = Numeric.ones( (9,1) ) print sum( a ) # Ok print sum( Matrix.Matrix( a ) ) # Fails