On Apr 1, 2005 7:12 PM, Douglas Bates <[EMAIL PROTECTED]> wrote: > I would like to create a method for the generic function "with" applied > to a class of fitted models. The method should do two things: > > 1. Substitute the name of the first argument for '.' throughout the > expression > > 2. Evaluate the modified expression using the data argument to the > fitted model as the first element of the search list. > > The second part is relatively easy. The default method for "with" has body > eval(substitute(expr), data, enclos = parent.frame()) > and you just change this to > eval(substitute(expr), eval(data$call$data), enclos = parent.frame()) > > So, for example > > > fm <- lm(optden ~ carb, Formaldehyde) > > with.lm <- function(data, expr, ...) eval(substitute(expr), > eval(data$call$data), enclos = parent.frame()) > > with(fm, carb) > [1] 0.1 0.3 0.5 0.6 0.7 0.9 > > However, I haven't been able to work out a clever way of using > substitute to get the first part. I would like to be able to call, e.g. > > with(fm, xyplot(resid(.) ~ carb)) > > and get a plot of resid(fm) ~ Formaldehyde$carb > > It is possible to do the first part by deparsing, substituting, and > parsing but that's inelegant. Can anyone suggest a more elegant method? > > BTW, the example of an lm model is just for illustration. The actual > use I have in mind is for lme (now lmer) models. The plot method for > the lme class in the nlme package does something very similar to this.
This seems to work, at least on your examples: > with.lm <- function(data, expr, ...) eval(substitute(expr), + append(model.frame(data), list(. = data)), parent.frame()) > > library(lattice) > data(Formaldehyde) > fm <- lm(optden ~ carb, Formaldehyde) > with(fm, carb) [1] 0.1 0.3 0.5 0.6 0.7 0.9 > with(fm, xyplot(resid(.) ~ carb)) ______________________________________________ R-devel@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
