On Tuesday, February 12, 2013 9:15:43 AM UTC+13, Eileen Tudaleft wrote: > bouloumag disgorged this amusing substitute for thought: > > > > > I would like to calculate the spatial derivative of a variable defined > > > on the points of a uniform grid. The domain is NOT periodic, so the FFT > > > method is useless here. > > > > really? > > > > Google: aperiodic FFT > > About 179,000 results (0.22 seconds) > > > > so all of that is entirely wrong? > > > > > I wonder if there exist other spectral methods > > > to calculate the derivative on an aperiodic domain or if my only hope is > > > to use the finite difference method? > > > > no, it's likely your 'other hope' is to spend some time thinking more carefully about your problem(s).
Yes, I was bemused by this post also. It implies that Kolmogorov's -5/3 law of turbulence and all other such work is rubbish. Perhaps OP is confusing non-periodic with non-stationary? FFT is not good for non-stationary data.