R help - Feb 2011 - retrieving partial residuals of gam fit (mgcv)

Dear list,


does anybody know whether there is a way to easily retrieve the so called
"partial residuals" of a gam fit with package mgcv? The partial
residuals are the residuals you would get if you would "leave out" a
particular predictor and are the dots in the plots created by

plot(gam.object,residuals=TRUE)

residuals.gam() gives me whole model residuals and
predict.gam(...,type='terms') only gives me the response function and
its standard deviation.

I would like to retrieve the values of these residuals as I would like to only
plot a random sample of the residuals to avoid overloading the plot (>100000
data points).


Thanks a lot in advance
Jannis

The partial residuals for a smooth term are just the whole model residuals + 
the corresponding estimate of the smooth term. You can use predict to access 
the latter and compute them quite easily. For example...

     set.seed(0) ## simulate some data...
     dat <- gamSim(1,n=400,dist="normal",scale=2)
     ## fit a model...
     b <- gam(y~s(x0)+s(x1)+s(x2)+s(x3),data=dat)
     fv <- predict(b,type="terms") ## get term estimates
     ## compute partial residuals for first smooth...          
     prsd1 <- residuals(b,type="working") + fv[,1]
     plot(b,select=1) ## plot first smooth
     ## add random selection of partial residuals
     ind <- sample(1:length(prsd1),100)
     points(dat$x0[ind],prsd1[ind],pch=19,col="pink") 


On Wednesday 16 February 2011 12:35, Jannis wrote:
> Dear list,
>
>
> does anybody know whether there is a way to easily retrieve the so called
> "partial residuals" of a gam fit with package mgcv? The partial
residuals
> are the residuals you would get if you would "leave out" a
particular
> predictor and are the dots in the plots created by
>
> plot(gam.object,residuals=TRUE)
>
> residuals.gam() gives me whole model residuals and
> predict.gam(...,type='terms') only gives me the response function
and its
> standard deviation.
>
> I would like to retrieve the values of these residuals as I would like to
> only plot a random sample of the residuals to avoid overloading the plot
> (>100000 data points).
>
>
> Thanks a lot in advance
> Jannis
>
>
>
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