| plot.gam {mgcv} | R Documentation |
Takes a fitted gam object produced by gam() and plots the
component smooth functions that make it up, on the scale of the linear predictor.
plot.gam(x,rug=TRUE,se=TRUE,pages=0,select=NULL,scale=-1,n=100,n2=40,
pers=FALSE,theta=30,phi=30,jit=FALSE,...)
x |
a fitted gam object as produced by gam().
|
rug |
when TRUE (default) then the covariate to which the plot applies is displayed as a rug plot at the foot of each plot of a 1-d smooth, and the locations of the covariates are plotted as points on the contour plot representing a 2-d smooth. |
se |
when TRUE (default) upper and lower lines are added to the 1-d plots at 2 standard errors above and below the estimate of the smooth being plotted while for 2-d plots, surfaces at +1 and -1 standard errors are contoured and overlayed on the contour plot for the estimate. If a positive number is supplied then this number is multiplied by the standard errors when calculating standard error curves or surfaces. |
pages |
(default 0) the number of pages over which to spread the output. For example,
if pages=1 then all terms will be plotted on one page with the layout performed automatically.
Set to 0 to have the routine leave all graphics settings as they are. |
select |
Allows the plot for a single model term to be selected for printing. e.g. if you just want the plot for the second smooth term set select=2. |
scale |
set to -1 (default) to have the same y-axis scale for each plot, and to 0 for a different y axis for each plot. |
n |
number of points used for each 1-d plot - for a nice smooth plot this needs to be several times the estimated degrees of freedom for the smooth. Default value 100. |
n2 |
Square root of number of points used to grid estimates of 2-d functions for contouring. |
pers |
Set to TRUE if you want perspective plots for 2-d
terms. |
theta |
One of the perspective plot angles. |
phi |
The other perspective plot angle. |
jit |
Set to TRUE if you want rug plots for 1-d terms to be jittered. |
... |
other arguments. |
Produces default plot showing the smooth components of a fitted GAM.
For plots of 1-d smooths, the x axis of each plot is labelled
with the covariate name, while the y axis is labelled s(cov,edf) where cov
is the covariate name, and edf the estimated (or user defined for regression splines) degrees of freedom of the smooth.
Contour plots are produced for 2-d smooths with the x-axes labelled with the first covariate
name and the y axis with the second covariate name. The main title of
the plot is something like s(var1,var2,edf), indicating the
variables of which the term is a function, and the estimated degrees of
freedom for the term. When se=TRUE, estimator variability is shown by overlaying
contour plots at plus and minus 1 s.e. relative to the main
estimate. If se is a positive number then contour plots are at plus or minus se multiplied
by the s.e. Contour levels are chosen to try and ensure reasonable
separation of the contours of the different plots, but this is not
always easy to achieve.
Within the function, the data for the plots is obtained by direct
calls to the compiled C code that predict.gam uses.
Smooths of more than 2 variables are not currently dealt with, but
simply generate a warning, but see vis.gam.
The function simply generates plots.
Note that the behaviour of this function is not identical to
plot.gam() in Splus.
The function can not deal with smooths of more than 2 variables!
Simon N. Wood simon@stats.gla.ac.uk
Gu and Wahba (1991) Minimizing GCV/GML scores with multiple smoothing parameters via the Newton method. SIAM J. Sci. Statist. Comput. 12:383-398
Wood, S.N. (2000) Modelling and Smoothing Parameter Estimation with Multiple Quadratic Penalties. J.R.Statist.Soc.B 62(2):413-428
Wood, S.N. (2003) Thin plate regression splines. J.R.Statist.Soc.B 65(1):95-114
http://www.stats.gla.ac.uk/~simon/
library(mgcv) set.seed(0) n<-200 sig2<-4 x0 <- runif(n, 0, 1) x1 <- runif(n, 0, 1) x2 <- runif(n, 0, 1) x3 <- runif(n, 0, 1) pi <- asin(1) * 2 y <- 2 * sin(pi * x0) y <- y + exp(2 * x1) - 3.75887 y <- y + 0.2 * x2^11 * (10 * (1 - x2))^6 + 10 * (10 * x2)^3 * (1 - x2)^10 - 1.396 e <- rnorm(n, 0, sqrt(abs(sig2))) y <- y + e b<-gam(y~s(x0)+s(x1)+s(x2)+s(x3)) plot(b,pages=1) # example with 2-d plots b1<-gam(y~s(x0,x1)+s(x2)+s(x3)) op<-par(mfrow=c(2,2)) plot(b1) par(op)