Re: combine_datasets

On Sun, Nov 16, 2003 at 14:25 -0500, John E. Davis wrote:
> Now, where to I go from here?  I suppose that I can do:
> 
>     s = get_data (d1); s.value[*] = 0; s.err[*] = 0;
>     d2 = define_counts (s);
>     d3 = define_counts (s);
>     assign_arf (a1, d1);
>     assign_arf (a2, d2);
>     assign_arf (a3, d3);
>     set_kernel ([d1,d2,d3], "gpileup");
>     () = combine_datasets ([d1,d2,d3]);
> 
> Will this work?  Is there a better way to do this?  I know that I can


As written, d2 and d3 will have non-zero uncertainties assigned
and those uncertainties will be summed in quadrature when the
datasets are combined.  This is probably not what you want.  

To work around this, you could set Minimum_Stat_Err=1.e-10 and 
use
  s.err[*] = 1.e-10
instead of zero.

Otherwise, this approach should work; offhand, I don't know of
a better way to do this.


[...]
> Incidently, I believe that the online help for combine_datasets has a
> a couple of typos, e.g.,
> 
>     combine_datasets (1,2, weights);
> 
> should probably be
> 
>     combine_datasets ([1,2], weights);


No, I think its correct as it stands -- either form should work.

Thanks,
-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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