Question

How can I sum an interval of elements on an array in python / numpy ?

For example, in matlab it is possible something like this:

y= ones(10,20);
y(1:5,:) = 2;
for k = 1: 10
   psum(k) = sum(y((1:3),k));
end

But sum function from numpy doesn’t suport “1:3”

Thanks !

Answer 1

Probably something like this:

y = numpy.ones((10, 20))
y[0:5] = 2
psum = y[0:3].sum(axis=0)

A simpler example:

y = numpy.array([2, 6, 7, 3, 4])
print y[1:4].sum()

prints 16, the sum of the middle three elements.