Heinz Tuechler wrote:
Hello,
still I have difficulties with variable names in functions. I know the
famous example form help for deparse/substitute but I will give a simpler
one to explain my problem.
I know from Reid Huntsinger (Tue, 8 Feb 2005 12:39:32 -0500) that:
"Semantically, R is pass-by-value, so you don't really have the names, just
the values. In implementation, though, R *does* pass names, in part at least
in order to do "lazy evaluation". You can get them via "substitute" ; see
the help for that."
The output of several functions does not make much sense, if these names do not appear (e.g. parameter estimates in Cox-regression, ...) Only to give a trivial example I show my problem with the table function.
As you know, if I call table as follows, the output is labelled properly.
charly<-c(rep(1,3),rep(2,7));delta<-c(rep(1:2,5)) table(charly, delta)
delta charly 1 2 1 2 1 2 3 4 If I define a trivial function to call table, the output is less satisfying. (Of course, I know that this function is useless.)
mytable1<-function(x,y){table(x,y)} mytable1(charly, delta)
y x 1 2 1 2 1 2 3 4 If I define the function in the following way, it does what I wish, namely it returns output equivalent to the simple call "table(charly, delta)".
mytable2<-function(x,y){
+ cat("table(",as.symbol((deparse(substitute(x)))), + "," , as.symbol(deparse(substitute(y))),")\n", + file="temp",sep="",append=F) + eval(parse("temp",n=-1)) + }
mytable2(charly, delta)
See argument "dnn" in ?table:
mytable2 <- function(x,y){ table(x, y, dnn = c(deparse(substitute(x)), deparse(substitute(y)))) }
Uwe Ligges
delta charly 1 2 1 2 1 2 3 4
I assume that there is a better way to solve this problem and I would be happy about hints, where to find solutions in the documentation.
Thanks,
Heinz T�chler
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