Fast Fourier Transform (FFT) in VBA

Can someone post the VBA code for the Fast Fourier Transform (FFT).
I need to rewrite it to do datasets larger than 4096 (Excel FFT is limited).
Looking for the same complex outputs that the built-in function provides.

Thanks in advance

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Google gave me this

https://stackoverflow.com/questions/...ing-excels-vba

i didn't look at the detail - but he seems to be asking for the same reason and have found a solution that he was happy with at the bottom.

Originally Posted by scottiex

Google gave me this

https://stackoverflow.com/questions/...ing-excels-vba

i didn't look at the detail - but he seems to be asking for the same reason and have found a solution that he was happy with at the bottom.

The above link from the Google search shows coding that uses WorkSheetFunctions (.Complex, .ImSum, .ImProduct, etc.)...
I'm looking for some version of raw code where every calculation is done within the same macro/script.
Or, I would settle for some code/psuedo code that walks me through the "real" & "imaginary" calculations as computed by Excel.
I have created the following code:

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Where FnCmplx is a 2D array of size (N-1,1) ... since the indexing starts at 0, and the array base is 0
i.e. for frequency kk=0, FnCmplx(0,0) = real number and FnCmplx(0,1) = imaginary number

However, when testing the script on a 4096 point data range - I have been unable to replicated the values that Excel produces.

I realize that my code above is not the FFT version of O(Nlog(N)) computations, but is instead the DFT expanded O(N^2) computations version...
But, the outputs should still be the same, correct??

If you are amenable to a formula-based solution, see attached. I expect it will get painfully slow with that many points.

Originally Posted by gth826a

VBA was miscalculating the Cos(2*pi*k*n/N) in some instances by .0000132262629816138 for integer-values of Pi.

Maybe you should use a more accurate representation of pi than

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