[Ifeffit] Re: ifeffit windowfunctions

[Matt Newville]

Hi Daniel,

On Wed, 11 Dec 2002, Daniel Grolimund wrote:

> In case I am using non-regularly spaced k-chi data, the plot of the
> chosen Fourier Transform Window is not represented correctly using the
> command plot(group.k, group.win)].
>
> Is there a way to get around that (except using interpolated and
> therefore regularly spaced) data?

Funny you mention this, I just noticed the same problem myself
over the weekend.  Currently, fftf() writes out the window
function assuming the 0.05 Ang-1 grid, regardless of the input
k-array.  I believe this is fixed (that is, the group.win array
corresponds to the group.k array!) in my latest test version.  I
still need to test other fixes in this version, but hopefully
I'll get it out early next week.

> Further, in a earlier version one had to use ikwindo = n to specify the
> Fourier Transform Window type. In ifeffit the termology kwindow = aaaaa
> is used. In addition to 'kaiser' and 'hanning' are there any other
> options for kwindow ?

Oh right. This is one place where Ifeffit and Feffit are
different.  Feffit's 'ikwindo = 2' caused some headaches (no one
could remember them!) so 'kwindow=hanning' etc seemed better (if
english-centric) for ifeffit.

Other window functions are 'parzen' (linear sills), 'welch'
(quadratic sills), and 'sine' (a sine wave over the whole range),
and 'gaussian' (which is really weird: centered at dk2, with full
width of 1/dk1, someone asked for it many years ago, it could
probably be improved!).

The next version of ifeffit will also have a window() command to
make window functions without actually doing the FTs.

--Matt