Calculate only fraction of spectrum with FFT

I have a signal with 4096 samples. I can calculate the frequency spectrum of this signal with fft. But I am only interested in a small fraction of the spectrum of about 40 specific frequency samples. Because I need to do this many many times, I need to get this as fast as possible. Any way? I tried to manually calculate the spectrum for those 40 samples, but fft is still faster. Thanks

Answer 1

[Darshan Ramakant Bhat]

MATLAB uses built-in multi threading for the fft command. So it will over-perform any user defined code for calculating fft points,even if one calculate for smaller number of points. You can also make your custom fft code faster by using parallel computing tool box. Following doc explains about it

https://www.mathworks.com/discovery/matlab-multicore.html

Regards,

Darshan Bhat