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Re: Need help in doing fft for a large matrix
Posted:
Feb 7, 2013 5:43 PM


On Friday, February 8, 2013 9:05:58 AM UTC+13, anyone wrote: > On Thu, 07 Feb 2013 11:06:42 0800, TideMan wrote: > > > > > On Friday, February 8, 2013 2:34:08 AM UTC+13, Gupta wrote: > > >> Hello...i ma trying to do abs(fft(y))) where y a large matriy of size > > >> 1x8388608. when i am running the code, at this line the program was > > >> getting terminated without running remaining commands. was the problem > > >> is with size of the matrix or memory of matlab or fft funtion. when i > > >> do this operation for a mtrix of size 1x4194304 it was working perfect. > > > > > > Why are you even trying to take the FFT of such a long series? > > > > My bet: that's what (s)he wants to do. > > > > > The resulting spectrum will be so noisy, you won't be able to interpret > > > it. > > > > Not necessarily, depends on signal content. > > > > > Split the signal into 10 or more blocks, take the FFT of each, then > > > average the results and take the abs of the first half. This will give > > > a nice smooth spectrum. > > > > ...and you necessarily lose detail on components that are relatively uncorrelated to a target signal. "A nice smooth > > spectrum" was not stated as any kind of requirement. My speculation: the OP has a hardware problem.
And my speculation: OP doesn't know what (s)he is doing and needs to think about what (s)he will get out of the transformation before buying new RAM.



