On Sep 16, 2012, at 11:27 PM, Christof Kluß wrote:
> Hi
>
> I would like to have something like
>
> str <- "df$JT == 12"
>
> fun <- function(df) {
>
> b <- eval(parse(str))
>
> return(b)
> }
>
What are you trying to do?
str <- quote(df$JT == 12)
> but for performance "eval(parse(a))" should not be evaluated at each
> function call, but should work as
>
> fun <- function(df) {
>
> b <- df$JT == 12
>
> return(b)
> }
>
> Do you have an idea how I can implement this?
Implement what? And what issues regarding "performance" are relevant? What
does it mean to "not evaluate at each function call"?
str <- quote(df$JT == 12)
fun <- function(df) {
b<-eval(str)
return(b)
}
df3 <- data.frame(JT=12)
fun(df3)
#[1] TRUE
--
David Winsemius, MD
Alameda, CA, USA
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