frames and formulas
Kevin Murphy <murphyk at cs.berkeley.edu> writes:
I can build a tree at the command line using
tr <- tree(V4 ~ ., dat)
but I don't know how to build one inside a function - the following does
not work
foo <- function(dummy) {
tr <- tree(V4 ~ ., dummy)
}
tr2 <- foo(dat)
and produces the error
Error in model.frame.default(formula = V4 ~ ., data = dummy) :
Object "dummy" not found
I know the solution has something to do with terms, formulas, frames,
environments, etc., but I can't figure it out (despite having read sec
3.4-3.5 of 'S progamming').
Jonathan Li reported the same thing just three days ago on R-help. It happens because tree uses the S-PLUS form of passing the frame number of the parent (i.e. eval(model, sys.parent())) rather than the parent environment, which conspires with an age-old bug in R that makes this work only on the command line. The quick fix is to modify the tree function to use eval(model, parent.frame()) instead. This is better R style anyway, but we'll get around to fixing eval() eventually.
O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._