Need help with matlab function interpretation related to Simpson' rule

Hey guys,

Got stuck with function integration using Simpson's rule:

The Matlab command related to it is:

for i=1:nr

u1d(i)=4.0*pi*r(i)^2*u(it,i)

end

I1=simp(0.0,r0,nr,u1d)/(4.0/3.0*pi*r0^3)

I1 is

http://s019.radikal.ru/i640/1302/0f/cb8012897da9.jpg

nr=21

r0=1.0;

Does it mean that I1 is integrated 21 times between boundaries 0 and r0?