for your info: ch. 11 mbe: fast fourier transforms

Robert Dodier wrote:
> On 5/2/09, Edwin Woollett <woollett at charter.net> wrote:
> 
>> I should have suggested, in my last reply, that I would be
>> available and eager to test your beta version of a new
>> fft and ift etc , which would also let me integrate my
>> package qfft.mac with the new versions.
> 
> OK, great. Just for the record, I'm going to make the fft functions
> handle lists as well as arrays, and also handle a single argument
> from which real and imaginary parts are extracted. I'm guessing
> these changes will make it easier to use.

Hi Robert, did you see my suggestions for the documentation of the fft 
routine about a month ago? The documentation made it seems like the 
frequencies involved were 0 to 2%pi radians per sample, but in fact they 
are 0 to %pi followed by -%pi up to -%pi/n which means that you can 
easily be confused if you are trying to use it to convolve something 
(like taking a derivative by multiplying each coefficient by omega)

I really appreciate your update of the FFT routines. They are extremely 
useful in solving PDEs and other numerical things. I, like you, think 
that maxima has a real strength in deriving results symbolically, and 
then plugging them into numerical schemes to get approximate results.

> I am also considering changing the name of the inverse function
> from ift to ifft, since it is the inverse of fft, not ft.
> What do you think of this name change? Another possibility is
> fft_inverse.

I think ifft makes the most sense, easy to type also.