[Ifeffit] Athena merging question...

[Bruce Ravel]

On Monday 17 September 2007, Matthew Ginder-Vogel wrote:
> When merging the energy scales of the various files, why did you
> choose to use a quadratic interpolation rather than a linear or spline
> interpolation?

Actually, you decide ;-)  In the preferences: General->intrp.

> Also, I notice that Athena sends a lot of commands that look like
>
> set vpkr.energy = vpkr.energy+0
> or
> set yybe.merge = qinterp(yybe.energy+0, yybe.xmu, vpkr.energy)
>
> to IFEFFIT when merging files.
>
> What does the +0 do at the end of the array?  I've been looking
> through the IFEFFIT documentation, but can't seem to find anything
> that clarifies that command. Also, if I try and issue the command at
> the IFEFFIT command line I get an error that reads "** cannot set
> scalar value to array **".  So why can Athena issue the command and I
> can't?

That would be because you are insufficiently cool ;-)

"0" is actually the value of the energy shift from the main window in
Athena.  When I say in the Athena documentation that the energy shift
is applied first and that the E0 value and all relative energy values
are on the shifted energy grid -- I actually mean that I am careful to
always add the energy shift whenever there is an Ifeffit command that
takes an energy array.

You should send a concise example of lines that give you the "**
cannot set scalar value to array **".  In principle, Ifeffit will add
a scalar to a vector en passant.  You shouldn't need to define a new
array just to hold that sum.  It might help to enclose the addition in
quotation marks, i.e.:

  set yybe.merge = qinterp("yybe.energy+1", yybe.xmu, vpkr.energy)

rather than

  set yybe.merge = qinterp(yybe.energy+1, yybe.xmu, vpkr.energy)

(You probably also want to use nore mnemonic groups names that
Athena's random four letter strings!)


HTH,
B


-- 
 Bruce Ravel  ---------------------------------------------- bravel at anl.gov

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