Example FFT Convolution

% matlab/fftconvexample.m
x = [1 2 3 4 5 6];
h = [1 1 1];

nx = length(x);
nh = length(h);
nfft = 2^nextpow2(nx+nh-1)
xzp = [x, zeros(1,nfft-nx)];
hzp = [h, zeros(1,nfft-nh)];
X = fft(xzp);
H = fft(hzp);

Y = H .* X;
y = real(ifft(Y))

Program output:

octave:10> fftconvexample
nfft = 8
y =
   1   3   6   9  12  15  11   6