[R] "Error : singular gradient matrix at initial parameters estimates"

[Mike Marchywka]

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> Date: Tue, 15 Feb 2011 09:43:25 +0100
> From: mariedidier1 at gmail.com
> To: r-help at r-project.org
> Subject: [R] "Error : singular gradient matrix at initial parameters estimates"
>
> Dear all,
>
> I am a fresh user of R and I already face to problems that I don't
> understand.
> In the use of the function nls(), I systematically have an error message :
> "Singular gradient matrix at initial parameters estimates".
> I tried to use nls() on a set of data that I subseted from a bigger matrix
> data. I wish to fit a gaussian on these points (spectrum) and draw this fit
> on the plot.
> Is this possible? Why do I always have this error message when using nls() ?

I guess this is because when it is evaluated at the initial parameter estimates
your gradient matrix is, well, singular :) Error messages are often not literally
accurate but in this case it would probably be good to start there. So, your
question is probably " how do I dump the initial parameter values and evaluate
the gradient matrix and determine what makes it pathological?" The first part being R
related, the second may or may not be. It could turn out just to be a typo making
something all zeroes maybe, or just badly conditioned etc. 



>
> Thank you for your answers, and don't make fun of me :) because, as I said,
> I am a fresh novice :)

I've gotten pretty good at trying to look for alternative questions in 
response to ill-defined ones such as, " are you an idiot?" LOL. 
If no one here makes fun of you eventually your data probably will 
or else you really haven't analyzed it enough :)