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Re: CURVEFIT.PRO standard deviations? [message #30632]

Mon, 13 May 2002 15:12

Ralf Flicker
Messages: 19
Registered: October 2001

Junior Member

William Thompson wrote:
>
[....]
> In the CURVEFIT program, the error bars are passed in through the
> WEIGHTS parameter in the calling sequence. There doesn't seem to be any
> way to make this optional. When you put in a WEIGHTS array of all ones,
> you're saying that the error in each point is +/- 1.0. If you put in
> more realistic weights, you'd get a more realistic error and
> chi-squared. With realistic weights, you should get a chi-squared of
> about one.

Yes, as Craig pointed out, I had overlooked the importance of the
weights and failed to set them to ~1/variance(data). Unfortunately,
in trying to find out what was wrong, I was confused further by
three fitting routines giving different answers for the same input.

Thanks y'all for your input, I'm just no statistics whiz kid :)

ralf

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[Message index]

		Re: CURVEFIT.PRO standard deviations? By: Ralf Flicker on Mon, 13 May 2002 15:12
		Re: CURVEFIT.PRO standard deviations? By: thompson on Mon, 13 May 2002 10:46
		Re: CURVEFIT.PRO standard deviations? By: Craig Markwardt on Mon, 13 May 2002 09:19
		Re: CURVEFIT.PRO standard deviations? By: Ralf Flicker on Mon, 13 May 2002 02:12
		Re: CURVEFIT.PRO standard deviations? By: Ralf Flicker on Mon, 13 May 2002 02:09
		Re: CURVEFIT.PRO standard deviations? By: Ivan Valtchanov on Mon, 13 May 2002 01:32
		Re: CURVEFIT.PRO standard deviations? By: Andrew Noymer on Sun, 12 May 2002 23:13

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