On Sep 22, 2009, at 5:07 PM, bamsel wrote:
Any help is very much appreciated. The following is a toy example:
#1. Create a data frame with two named columns (x,y):
DF <- data.frame(cbind(x=1:5, y=6:10))
DF
x y
1 1 6
2 2 7
3 3 8
4 4 9
5 5 10
#2. Define a function to compute the sum of a given column:
foo.fnc = function(i){
+ return(sum(DF[ ,i]))
+ }
#3. Call the function to get the mean of column 1, for example:
foo.fnc(1)
[1] 15
# Now, what I really want is to be able to use a column name as the
argument
# That is, something like:
# foo.fnc = function(colname)
# And calling it:
# foo.fnc(DF$x)
That would just be giving the column vector itself to the function, so
the function could be as simple as:
foo.fnc <- function(x) sum(x)
Had you wanted to give two arguments, it could be thus:
> foo2.fnc <- function(dfrm, cname) sum(dfrm[,cname])
> foo2.fnc(DF, "x")
[1] 15
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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