On Thu, 2011-04-28 at 23:08 -0400, Chee Chen wrote: > Dear All, > I would like to define a function: f(x,y,z) with three arguments x,y,z, such > that: given values for x,y, f(x,y,z) is still a function of z and that I am > still allowed to find the root in terms of z when x,y are given. > For example: f(x,y,z) = x+y + (x^2-z), given x=1,y=3, f(1,3,z)= 1+3+1-z is > a function of z, and then I can use R to find the root z=5. > > Thank you. > -Chee
Interesting exercise. I've got this function, which I think it's doing what you're asking. f <- function(x,y,z) { fcall <- match.call() fargs <- NULL if(fcall$x == "x") fargs <- c(fargs, "x") if(fcall$y == "y") fargs <- c(fargs, "y") if(fcall$z == "z") fargs <- c(fargs, "z") ffunargs <- as.list(fargs) names(ffunargs) <- fargs argslist <- list(fcall) ffun <- append(argslist, substitute( x+y + (x^2-z) ), after=0)[[1]] as.function(append(ffunargs, ffun)) } This yields. > f(3, 2, z) function (z = "z") 3 + 2 + (3^2 - z) <environment: 0x132fdb8> > f(3, 2, z)(3) [1] 11 I haven't figured out how to get rid of the default argument value shown here as 'z = "z"'. That doesn't prevent it to work, but it's less pretty. If you find a better way, let me know. HTH, Jerome ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.