scam (version 1.1-1)

vis.scam: Visualization of SCAM objects

Description

Produces perspective or contour plot views of scam model predictions. The code is a clone of vis.gam of the mgcv package.

Usage

vis.scam(x,view=NULL,cond=list(),n.grid=30,too.far=0,col=NA,
        color="heat",contour.col=NULL,se=-1,type="link",
        plot.type="persp",zlim=NULL,nCol=50,...)

Arguments

x

a scam object, produced by scam()

view

an array containing the names of the two main effect terms to be displayed on the x and y dimensions of the plot. If omitted the first two suitable terms will be used.

cond

a named list of the values to use for the other predictor terms (not in view). Variables omitted from this list will have the closest observed value to the median for continuous variables, or the most commonly occuring level for factor

n.grid

The number of grid nodes in each direction used for calculating the plotted surface.

too.far

plot grid nodes that are too far from the points defined by the variables given in view can be excluded from the plot. too.far determines what is too far. The grid is scaled into the unit square along with the view

col

The colours for the facets of the plot. If this is NA then if se>0 the facets are transparent, otherwise the colour scheme specified in color is used. If col is not NA then it is used as t

color

the colour scheme to use for plots when se<=0. one="" of="" "topo", "heat", "cm", "terrain", "gray" or "bw". Schemes "gray" and "bw" also mod

contour.col

sets the colour of contours when using plot.type="contour". Default scheme used if NULL.

se

if less than or equal to zero then only the predicted surface is plotted, but if greater than zero, then 3 surfaces are plotted, one at the predicted values minus se standard errors, one at the predicted values and one at the predicted val

type

"link" to plot on linear predictor scale and "response" to plot on the response scale.

plot.type

one of "contour" or "persp".

zlim

a two item array giving the lower and upper limits for the z-axis scale. NULL to choose automatically.

nCol

The number of colors to use in color schemes.

...

other options to pass on to persp, image or contour.

Value

• Simply produces a plot.

See Also

persp, vis.gam, and scam.

Examples

library(scam)

# Example with factor variable
set.seed(0)
fac<-rep(1:4,20)
x <- runif(80)*5;
y <- fac+log(x)/5+rnorm(80)*0.1
fac <- factor(fac)
b <- scam(y~fac+s(x,bs="mpi"))

vis.scam(b,theta=-35,color="heat") # factor example

# Example with "by" variable

z<-rnorm(80)*0.4   
y<-as.numeric(fac)+log(x)*z+rnorm(80)*0.1
b<-scam(y~fac+s(x,by=z))
g <- gam(y~fac+s(x,by=z))

vis.scam(b,theta=-35,color="terrain",cond=list(z=1)) # by variable example
vis.scam(b,view=c("z","x"),theta= 65) # plot against by variable