[R] gam plots

Simon Wood snw at mcs.st-and.ac.uk
Sat Dec 22 16:29:28 CET 2001


> I would like postscript gam plots for the two smoothed terms to be 
> produced on separate pages, but am having trouble getting these.  I 
> can get the two plots output to a single page using
> 
> >  postscript("gams.ps")
> >  plot(mymodel.gam, pages=1, se=T)
> >  dev.off()
> 
> I don't want this, but when I try replacing pages=1 with pages=2, I 
> still get only one page in the postscript file with the second plot 
> overlaid on the first one:
> 
> >  plot(mymodel.gam, pages=2, se=T)
> Press return for next page....
> 
.... I can't get this to happen, but i don't have access to a mac at the
moment [I tried it using R 1.4.0 / mgcv 0.6.* under unix]. I wonder if the
problem is Mac specific?

> I also noticed that the plot gives tick marks for the values of the 
> variable along the horizontal axis, but I would like a rug of *all* 
> the values (Splus5 produces a rug using jittering to show the density 
> of the observations, but the version of R that I have doesn't do 
> this, as far as I can tell).

- sorry, jittering's not implemented, but it should be easy to get a
jittered plot. Your model object will contain all the raw data in
mymodel.gam$x (in addition to any dummy variables implied by the model
formula). You can jitter these yourself before calling plot.gam(). e.g. to
jitter the second covariate:

mymodel.gam$x[2,]<-jitter(mymodel.gam$x[2,])

[although you probably want to control the amount of jittering using the
`amount' argument]. I'll add adding a jitter option to the mgcv "to
do" list. 

Simon

  ______________________________________________________________________
> Simon Wood  snw at st-and.ac.uk  http://www.ruwpa.st-and.ac.uk/simon.html
> The Mathematical Institute, North Haugh, St. Andrews, Fife KY16 9SS UK
> Direct telephone: (0)1334 463799          Indirect fax: (0)1334 463748 




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