matlab: convolution function

function [n,y] = convm(x,nx,h,nh)
y = conv(x,h);
n = [nx(1)+nh(1):nx(1)+nh(1)+length(y)-1];
end

The starting number of the convolutional sequence = the starting number of the two convolutional sequences and

y = conv(a,b)

conv also does polynomial multiplication. y(x)=a(x)*b(x)