[R] Adding groups to regression line panel function in Lattice

Deepayan Sarkar
2011-09-12T04:16:02Z

On Fri, Sep 9, 2011 at 9:38 PM, Bigelow, Seth <sbigelow at fs.fed.us>
wrote:
> I wish to display a single-panel Lattice figure with grouped data and
fitted regression lines. I don't seem to be able to get the
> individual regression lines to display, e.g.;
>
> d <- data.frame(q = rep(1:6, each=10), cc = rep(seq(10,100, 10),6)) ? ?
? ? ? ? ? ? ? ? ? ? ?# create data frame with group identifier 'q',
independent variable cc
> d$ba = d$q*0.1*d$cc + 5*rnorm(nrow(d)) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? # create dependent variable 'ba'
>
> mypanel <- function(...){ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?# panel function
> ? ? ? ? ? ? ? ?panel.lmline(d$cc, d$ba, groups = d$q) ? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?#
> ? ? ? ? ? ? ? ?panel.xyplot(...)
> ? ? ? ? ? ? ? ?}

But panel.lmline() does not honour a 'groups' argument, so there is no
reason for this to work.

> xyplot(ba~cc,d,
> ? ? ? ? ? ? ? ?groups=q,
> ? ? ? ? ? ? ? ?panel = panel.superpose,
> ? ? ? ? ? ? ? ?panel.groups=mypanel
> ? ? ? ? ? ? ? ?)
>
> Can anyone suggest how to get lines to display by group?

How about

xyplot(ba~cc,d, groups=q, type=c("p", "r"))

> (and how to get lmline panel to fit line without estimating an intercept?)

xyplot(ba~cc,d, groups=q, panel = panel.superpose,
       panel.groups = function(x, y, ...) {
           panel.xyplot(x, y, ...)
           panel.abline(0, coef(lm(y ~ 0 + x)), ...)
       })

-Deepayan