[R] Executing a Function in a Loop With a Changing Value foran Argument

[Bill.Venables at csiro.au]

There are many simple ways to do this, if I understand you correctly.
Here is an example

> dat <- data.frame(matrix(rnorm(25), 5, 5))
> names(dat)
[1] "X1" "X2" "X3" "X4" "X5"
> vars <- names(dat)[-1]
> vars
[1] "X2" "X3" "X4" "X5"
> myfunc <- function(x) print(mean(x))
> for(i in dat[, vars]) myfunc(x = i)
[1] 0.3648022
[1] -0.1593466
[1] 0.5874517
[1] -0.5049586
> colMeans(dat)  ## as a check
        X1         X2         X3         X4         X5 
 0.1779146  0.3648022 -0.1593466  0.5874517 -0.5049586 
> 


Bill Venables
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-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Rick Bilonick
Sent: Thursday, 25 October 2007 3:02 PM
To: R Help
Subject: [R] Executing a Function in a Loop With a Changing Value foran
Argument

I want to run a function in a loop and replace one of the arguments from
a large list each time through the loop. If I was writing it out
manually:

myfunc(x=var1)
myfunc(x=var2)
etc.

But I want to do this in a loop where x is replaced by a new name. 

Something like:

for(i in vars) { myfunc(x=i) }

where "vars" is a vector of names for items in a data.frame.

If I use "as.symbol" to create names, the evaluation never works
correctly. Is there a way to do this? Any suggestions would be
appreciated.

Rick B.

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