# [R] Lattice: groups and no groups with panel.superpose

Robert Buitenwerf buitenwerfrobert at hotmail.com
Sat Nov 15 15:25:39 CET 2008

Dear R listers,

I am trying to create a lattice plot with independent regression lines per group
for each panel, plus one overall regression line per panel. I succeed in having
the separate regression lines for each group per panel, but I can't figure out
how to add the overall regression line over all groups. I have learnt a lot from
the list, but I can't find an example for what I want to do...

with the following example data (from another post):
years<-2000:2006
weeks<-1:20
yr<-rep(years,rep(length(weeks)*6,length(years)))
wk<-rep(weeks,rep(6,length(weeks)))
temp<-rep(4:9,length(years)*length(weeks))
yvar<-round(rnorm(length(years)*length(weeks)*6,mean=30,sd=4),0)
xvar<-(rnorm(length(years)*length(weeks)*6)+5)/10
df<-data.frame(year=yr,week=wk,temp=temp,       yvar=yvar,
xvar=xvar)

I get the regression lines per group for each panel using:

xyplot(yvar~year|week,data=df,layout = c(4, 5),
type='p',
groups = temp ,
panel = panel.superpose,
panel.groups = function(x, y, ..., lty) {
panel.xyplot(x, y, ..., lty = lty)
panel.abline(lm(y~x), lty=3, ...)
})

And obviously the overall regression lines with:

xyplot(yvar~year|week,data=df,layout = c(4, 5),
type='p',
panel = function(x, y, ...) {
panel.xyplot(x, y, ...)
panel.abline(lm(y~x))
})

Any advice on how to "merge" the output from the two above graphs would be
greatly appreciated!

Kind regards,

Robert Buitenwerf
Ecologist
SAEON
South Africa
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