# Re: writing out data

From: John Houck <houck>
Date: Sat, 9 Nov 2002 19:51:23 -0500
```On Sat, Nov 09, 2002 at 19:32 -0500, Saku Vrtilek wrote:
>
> Thanks to John Houck I am able to write out my model and data:
>
> m = get_model_counts(1);
> writecol ("filename.ascii", m.bin_lo, m.bin_hi, m.value);
>
> However, athough the plot that I see when using rplot_counts is
> counts vs energy the ascii file has counts vs wavelength.  Can
> someone tell me how to get counts vs energy?

The function _A() can be used to convert back and forth
between wavelengths in Angstroms and energies in keV.
For example:

isis> e=[1:3];
isis> print(_A(e));
4.132806e+00
6.199209e+00
1.239842e+01

isis> print(_A(_A(e)));
1.000000e+00
2.000000e+00
3.000000e+00

isis>

If given two vectors, it interprets them as bin_lo,bin_hi and
automatically swaps the order. So, to get counts vs. energy:

(elo, ehi) = _A (m.bin_lo, m.bin_hi);
writecol ("filename.ascii", elo, ehi, reverse(m.value));

Note that its necessary to reverse the order of the
bin-value array to match the energy grid:

isis> e=[1:3];
isis> v = [4,3,1];
isis> writecol (stdout, e, v);
1             4
2             3
3             1
isis> writecol (stdout, _A(e), reverse(v));
4.13281             1
6.19921             3
12.3984             4

>
> Also how to get counts/sec/kev
>

To get counts/sec/keV, just divide by the exposure time
and bin-width:

t = get_arf_exposure(1);   % or you might use get_data_exposure(1)

(elo, ehi) = _A (m.bin_lo, m.bin_hi);
e_width = ehi - elo;

e_value = reverse(m.value);

writecol ("filename.ascii", elo, ehi, e_value / t / e_width);

-John

--
John C. Houck                       MIT Center for Space Research
NE80-6005: 617-253-3849                   77 Massachusetts Avenue
42:21:55.105N, 71:05:28.122W             Cambridge, MA 02139-4307
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Received on Sat Nov 09 2002 - 19:51:26 EST

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