Pass string variable into R function

Question

I want to pass a variable name into a function and can't seem to do it. Simply...

library (reshape)
test <- function(x) {
 cast(data, x ~ ., length)
}
test(ageg)

I get this kickback.

Error: Casting formula contains variables not found in molten data: x

I know it's simple but I can't find the answer.I want it to simply run

cast(data, ageg ~ ., length)

Can you please put the name of the package you used at the begining of your code to make it more reproductible. Thks — dickoa
– dickoa, Commented Jul 16, 2013 at 21:07

asb · Accepted Answer · 2013-07-16 20:19:11Z

2

Try this:

test <- function (x) cast(data, as.formula(paste0(x , " ~ .")), length)

What you are trying to do is write a formula on the fly. However, a formula is possed on as quoted part of the language (IIRC). Therefore, your x is not evaluated but looked for in your data as x.

What this does on the other hand is to first create a character string by evaluating x in paste0. Then the string is converted to a formula using as.formula.

answered Jul 16, 2013 at 20:19

asb

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