#acl All:read

== Plotting two models fit to a spectrum ==

Suppose we have separately fit two different models to a single spectrum and for illustrative purposes want to include them in the same plot. To do this we need to define two sources which we do as follows. Suppose the spectrum is example.pha and its response example.rsp. Then

{{{
XSPEC12> data example.pha
XSPEC12> resp example.rsp
XSPEC12> resp 2:1 example.rsp
}}}

This defines two sources, both using example.rsp as their response. We now load in both the models, with their parameter values as determined previously in the separate fits.

{{{
XSPEC12> model phabs(pow)
...
XSPEC12> model 2:second phabs(pow + ga)
...
}}}

We now do the standard plot

{{{
XSPEC12> cpd /xs
XSPEC12> iplot data
PLT>
}}}

At this point the plot contains the data, the sum of the two models, and the two models. Obviously, we don't want the sum of the two models so we will set that to colour 0.
We can also change the colour on the second model to make clear which is which

{{{
PLT> col 0 on 2
PLT> col 2 on 4
}}}

To plot the the model fits without the data just use iplot foldmodel instead of iplot data. To plot both models in model space the following can be used

{{{
XSPEC12> plot model model second
PLT> plot over
PLT> view 0.1 0.1 0.9 0.9
PLT> col 2 on 2
}}}