[R] Using data and subset arguments in user-defined functions

From: Manuel Morales <Manuel.A.Morales_at_williams.edu>
Date: Fri 27 Oct 2006 - 21:18:05 GMT


Dear list,

A while ago, I posted a question asking how to use data or subset arguments in a user-defined function. Duncan Murdoch suggested the following solution in the context of a data argument:

data <- data.frame(a=c(1:10),b=c(1:10))

eg.fn <- function(expr, data) {

                  x <- eval(substitute(expr), envir=data)
                  return(mean(x))

}

eg.fn(a,data)

I've tried various approaches to add a subset argument to the example above, but no luck. I'm looking for something like the following (but that works!)

eg.fn2 <- function(expr, data, subset) {

                   data <- subset(data,subset)
                   x <- eval(substitute(expr), envir=data)
                   return(mean(x))

}

eg.fn2(a, data, subset=a>3)

This returns the error:
"Error in eg.fn2(a, data, subset = a > 3) :

        object "a" not found"

Any suggestions?

Thanks!

-- 
Manuel A. Morales
http://mutualism.williams.edu

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Received on Sat Oct 28 07:26:29 2006

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