[R] passing variable names to dplyr - SOLVED

[Bos, Roger]

All,

I asked over at the manipulatr group and Hadley showed me how to do it.  In case anyone is interested I will post the solution here:

target <- "hp"
call <- substitute(mutate(mtcars, scale(target)), list(target = as.name(target)))
eval(call)

Thanks,

Roger

-----Original Message-----
From: arun [mailto:smartpink111 at yahoo.com]
Sent: Monday, January 27, 2014 5:25 PM
To: Bos, Roger
Subject: Re: [R] passing variable names to dplyr

Hi Roger,

This works on library(plyr), but not in dplyr.

target <- "hp"
res2 <- plyr:::mutate(mtcars,hp1= eval(parse(text= sprintf("scale(as.numeric(%s))",target))))
A.K.




On Monday, January 27, 2014 10:47 AM, "Bos, Roger" <roger.bos at rothschild.com> wrote:
All,

I would like to figure out how to pass variable names to the dplyr function mutate.  For example, this works because hp is one of the variable names on mtcars:

mutate(mtcars, scale(hp))

Let's says I want to pass in the target variable instead of hard-coding the name, as follows:

target <- "hp"
mutate(mtcars, scale(target))

That dones't work.  I read somewhere about using lapply, but that suggestion didn't work for me either:

target <- lapply("hp", as.symbol)
mutate(mtcars, scale(target))

Does anyone know how to do this?

Thanks,

Roger

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