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From: Matt J on 17 Feb 2010 11:44
"Matt J " <mattjacREMOVE(a)THISieee.spam> wrote in message <hlh41o$sjs$1(a)fred.mathworks.com>...
you suggest to time shift then.
>
> interp1(t,x,t+t0)
>
> This is an O(N) computation using only real arithmetic, whereas with FFTs it's
> an O(N*logN) computation using complex arithmetic.

Actually, interp1() has a lot of overhead in it, because it has to handle non-uniform spacing as well as a lot of extra functionality. I would recommend conv() instead. To give you an idea of the difference, the following compares, roughly, the operations in a t0=0.5 shift using the two methods:

N=1e6;
dt=1;
fAxis=ifftshift((0:N-1) -ceil((N-1)/2))/N/dt;

y=rand(1,N);
t0=.5;

tic;
z=ifft(fft(y).*exp(-j*2*pi*t0*fAxis));
toc;
%Elapsed time is 0.283069 seconds.

clear z;

tic;
z=(conv(y,[t0,1-t0]));
toc;
%Elapsed time is 0.032134 seconds.
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