Re: issue plotting Flux of a data set

On Nov 10, 2010, at 11:03 PM, Freddy Martinez wrote:

> I loaded a simple pha file ('heg_1.pha) and plotted it using
> plot_data_counts() and was able to get the data to plot (on a log
> scale). When I try to plot the flux of the data, I get an error in
> isis:
> 
> isis> plot_data_flux(1);
> Invalid: plot limits
> Error: plot failed
> 
> I'm not sure what I'm missing as I'm just now learning to use isis in
> my research.  Whats the best way to plot flux versus energy in isis.

Ah, welcome to the wonderful world of ISIS!  Actually, you've found
me right now programming up a simple script to rename the "gauss"
function to the names of pre-specified lines (e.g., Ne9r, Ne9i, Nef),
and then sort them into ascending wavelength order in your fit 
function.  (Manfred - I'm sure you'll tell me that you've already done
this.)  Lots of fun things you can do with ISIS.

Anyhow, plot_data_flux assumes that you have "flux corrected" the data
using the flux_corr function.  "Flux correction" in X-ray astronomy is
an inherently slightly naughty thing to do, thanks to the response matrices
involved.  However, it's not *so* horrible for gratings spectra, as the responses
are nearly diagonal matrices (i.e., the flux correction is reasonably accurate).

At any rate, I have written a set of higher level plotting functions for ISIS, which
you can grab from here:

	http://space.mit.edu/home/mnowak/isis_vs_xspec/

The plot_unfold function should pretty much do what you want, with lots
of choices for units.  If you have any problems with that,  just drop us a line.

Cheers,

Mike Nowak
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