Fast Fourier Transform help..

[Guest]

Can anyone offer us a suggestion on where to find information about FFT in
Excel?

The VBA Analysis Toolpak offers a function called ATPVBAEN.XLA!Fourier .

We'd like to know more about it's parameters and abilities.
We want to convert a time domain force vector into REAL force versus
frequency for the binary data segment.

 

[Dana DeLouis]

We'd like to know more about <Fourier> parameters and abilities.

Do you have any specific questions? It's a Radix-2 Algorithm only.
Arbitrarily limited to 2^12, or 4096 data points. It's a Subroutine, and
can only be called with data on a worksheet. (Too bad...best to have your
own fft program in vba). VBA editor "debug.print" statements in previous 2
versions caused this to run extremely slow. Fixed in 2007. Can work with
either "i" or "j" complex strings (ie 2+3i or 2+3j).
The frequency domain includes all the data (good for signal processing, etc)
but to do data analysis etc you need to divide by the size of the data.
[for example, use IMDIV( ) ].
Another annoyance for the spreadsheet interface is that blank cells are not
treated as zero. FFt will trigger an error with blank cells.
The algorithm itself is really good though.

 

[Guest]

Hello, Dana,

I'm the one that posted, but not the one that wanted to use it, so I don't
know the specific question. Thanks for your post. I will pass it along to
the person who wanted it on Monday.

How I got involved is that the company Help Desk has me listed as the local
Excel expert.

Thanks,
Mark