Dear Dr. Gavin,

Thank you very much for your help. All my data are unique (because I have 56
different stations). As you suggest I restrict the
complexity of the individual smooths:

response ~ s(Lat, k = 9) + s(Long, k = 9) + s(deep, k = 9)

Problem solved.

Now I try to make other model:

 modelo2<-gam(Density~s(year, k=6)+s(Month, k=6)+s(rainfall, k=6),
family=Gamma, data=at)

The "new" problem is that R give me the next error  *"Error en
smooth.construct.tp.smooth.spec(object, dk$data, dk$knots) :
  A term has fewer unique covariate combinations than specified maximum
degrees of freedom"*.

Anybody knows what mean this?

Regards.

2011/5/18 Gavin Simpson <gavin.simpson@ucl.ac.uk>

> On Wed, 2011-05-18 at 10:53 -0500, ARISTIDES LOPEZ wrote:
> > Dear members list,
> >
> > I'm trying to make a model for descrive the distribution of demersal
> fishes
> > in the Colombian Caribbean Sea. I have a data set of n= 56, the model is
> > like this: Density (ind/km2) ~ s(Lat) + s(Long) + s(deep). The problem is
> > that R give me the error message *"Model has more coefficients than
> data"*.
> >
> > Anybody knows how can avoid this?
> >
> > Faithfully.
>
> Each of your smooths will be using k = 10 degrees of freedom so that is
> 30 degrees of freedom already, which is a lot for a data set of 56
> observations.
>
> Are all the data unique? i.e. you have 56 unique density values, 56
> unique lats, 56 unique lons etc. If not, it might be the the unique
> information in the data is not sufficient to support the complexity of
> the smooths.
>
> My money would be on that you did something you haven't actually told
> us, and have more smooths in the model than you say and they are using
> more degrees of freedom than it appears to us.
>
> The easy way to try to solve the problem, will be to restrict the
> complexity of the individual smooths:
>
> response ~ s(Lat, k = 6) + s(Long, k = 6) + s(deep, k = 6)
>
> for example.
>
> You could probably model these data as a Possion with an offset term for
> the km2 covered by each sample, rather than treating these as a density.
>
> HTH,
>
> G
>
> --
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>  Dr. Gavin Simpson             [t] +44 (0)20 7679 0522
>  ECRC, UCL Geography,          [f] +44 (0)20 7679 0565
>  Pearson Building,             [e] gavin.simpsonATNOSPAMucl.ac.uk
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>
>


-- 
Aristides López-Peña

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