[Ifeffit] Ifeffit: spline with a standard

[Matt Newville]

Hi Michael,

This seems like a question that others might have, so I hope
it's OK that I'm sending this reply to the ifeffit mailing
list too.

On Thu, 23 May 2002, Michael Green wrote:

> I can't figure out how to use a standard for background
> removal in G.I.FEFFIT or IFEFFIT.  Is there a way to do
> this?  Table 4 of the Refman lists a chi_std data type, but
> I didn't find any mention of it anywhere else.

Yes.  In ifeffit, it would go like this:

  ####
  # background-removal using known chi(k) data
   read_data(file= data.xmu,     label= 'energy xmu', group= dat)
   read_data(file= standard.chi, label= 'k chi ',     group= std)

  # without standard
   spline(energy= dat.energy, xmu= dat.xmu, kweight=1,rbkg=1)

  # with standard
   spline(energy= dat.energy, xmu= dat.xmu, kweight=1,rbkg=1,
          k_std=std.k, chi_std = std.chi)
  ####

That is, you read in the spectra for the standard, and use it's
"k" and "chi" arrays for "k_std" and "chi_std".

Hope that helps,

--Matt