[R] Grasper model error

Simon Wood s.wood at bath.ac.uk
Wed Aug 16 11:07:38 CEST 2006

I'm not too familiar with using grasp, but the error is generated from the 
`mgcv' package while setting up a GAM. The default smooths used for `s' terms 
by mgcv::gam are thin plate regression splines based on an `eigen 
approximation' to full thin plate splines. These have some nice properties 
but become expensive to set up for data sets with more than a few thousand 
points, in which case it is better to use a different basis for smooths of 
one variable, e.g.
or for smooths of several variables use either tensor product smooths, e.g.
or use the `knots' argument to `gam' in the way shown at the end of the 
examples in the `gam' help file.


On Tuesday 15 August 2006 19:29, Ken Nussear wrote:
> I tried this over a the grasp users yahoo group and got no
> response....So I wonder if anyone here knows about grasper
> I keep getting this error when trying to run a model.
> Error in smooth.construct.tp.smooth.spec(object, data, knots) :
> Too many knots for t.p.r.s term: see `gam.control' to increase limit,
> or use a
> different
> basis, or see large data set help for `gam'.
> I'm using R for OSX Gui Version 1.16 R-version 2.3.1, running grasper
> version
> 0.4-4
> My dataset has ~7500 rows of input, and 21 cols of input.
> Does anyone have an idea how to troubleshoot this?
> Thanks
> Ken
> 	[[alternative HTML version deleted]]
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> Simon Wood, Mathematical Sciences, University of Bath, Bath, BA2 7AY UK
> +44 1225 386603  www.maths.bath.ac.uk/~sw283

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