ARE: [Ifeffit] Re: Ifeffit Digest, Vol 5, Issue 1

Bruce Ravel ravel at
Mon Jul 7 12:11:08 CDT 2003

On Monday 07 July 2003 12:45 pm, Matt Newville wrote:
> Anyway, I think using the 'epsilon_k' that chi_noise() estimates as
> the noise in chi(k) is a fine way to do a weighted averages of data.
> It's not perfect, but neither is anything else.

Exactly right!  As Matt explained, there are reasons to believe that
the measurement uncertainty is dominated by things that Parsival's
theorem doesn't address and that measuring those problems is hard.

As Matt said, weighting by 1/chi_noise() is OK.  As Scott said,
weighting uniformly is OK.  Those are two choices are the most OK I
can think of, so Athena will let you choose between them.

While I am of the chorus of people agreeing with Grant that mu is not
equal to <If>/<I0>, I can see no reason why Athena should actively
prevent the user from looking at <If> or <I0>, if that is what he
wants to do.  The *current* version of Athena prevents this, but
that's a bug not a feature! ;-)


 Bruce Ravel  ----------------------------------- ravel at
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