Mac OS 10.3.9 R framework v. 2.1.1
I am attempting to put a fitted curve into each panel of a lattice
graph, but am failing to do so. I have tried writing a very
sophisticated function to do so. The function seems to work when used
with plot(), but does not do so inside a panel function in xyplot().
Any pointers would be appreciated.
#The example data
fact <- gl(2,7)
x <- rep(1:7,2)
y <- c(1,1,2,3,2,3,4,1,2,1,2,3,3,4)
plot(jitter(y/6) ~ x)
# The following user defined function puts a curve (I believe the
correct one) into the scatterplot
panel.predglm <- function(x, y) {
model.trial <- glm(cbind(y,6-y) ~ poly(x,2),
family=quasibinomial(link="logit"))
xfit <- seq(1,7, length=21)
yfit <- predict(model.trial, newdata=data.frame(x=xfit),
type="response")
lines(xfit,yfit) }
panel.predglm(x, y)
# My attempt to use it in a lattice xyplot, however, fails. It draws a
curve which in most cases is outside the dimensions of the plot. I
suspect that the prediction is on the scale of the link functions.
library(lattice)
xyplot(y/6 ~ x|fact, ylim=c(0,.8),
panel=function(x, y,...) {
panel.xyplot(jitter(x),jitter(y))
panel.predglm(x,y) }
)
Any thoughts?
Hank Stevens
Dr. Martin Henry H. Stevens, Assistant Professor
338 Pearson Hall
Botany Department
Miami University
Oxford, OH 45056
Office: (513) 529-4206
Lab: (513) 529-4262
FAX: (513) 529-4243
http://www.cas.muohio.edu/botany/bot/henry.html
http://www.muohio.edu/ecology/
http://www.muohio.edu/botany/
"E Pluribus Unum"
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