Re: [R] least square fit with non-negativity constraints for absorption spectra fitting

From: Dieter Menne <dieter.menne_at_menne-biomed.de>
Date: Fri 14 Jul 2006 - 22:43:19 EST

Xu, Xiuli (NIH/NHLBI) [E] <xux3 <at> nhlbi.nih.gov> writes:

>
> I would really appreciate it if someone can give suggestions on how to
> do spectra fitting in R using ordinary least square fitting and
> non-negativity constraints. The lm() function works well for ordinary
> least square fitting, but how to specify non-negativity constraints? It
> wouldn't make sense if the fitting coefficients coming out as negative
> in absorption spectra deconvolution.

I don't see much reasons to use lm() to fit a spectrum, but if you want to do that, negative coefficients simply mean a shift by pi, sothe sign can be discarded for most practical purposed.

But better look at one of the specialized packages like spectrino.

Dieter



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