[Ifeffit] FFT in Ifeffit

[Scott Calvin]

Hi Matt,

As I was working on my talk for the EXAFS workshop, I came across a 
rather technical question: how does Ifeffit choose the number of 
points for the Fourier transforms? As I recall, FEFFIT used an 
algorithm which required an integer power of 2, so its default 
behavior was to use the smallest integer power of 2 greater than the 
number of points in the chi(k) data, and then pad the rest with 0's. 
This default behavior could also be over-ridden if desired.

It doesn't look to me like Ifeffit is handling that in the same 
way--is it always using a very large number of points and padding 
with 0's, or is it using an algorithm that doesn't require the 
integer power of 2, or is it interpolating the chi(k) on to a grid of 
the appropriate size first, or...?

I appreciate any info you can give me on this.

--Scott Calvin
Sarah Lawrence College