Broadcasting is really good for this:
row_sums = a.sum(axis=1)
new_matrix = a / row_sums[:, numpy.newaxis]
row_sums[:, numpy.newaxis]
reshapes row_sums from being (3,)
to being (3, 1)
. When you do a / b
, a
and b
are broadcast against each other.
You can learn more about broadcasting here or even better here.