[R] Character string to R object

[Gabor Grothendieck]

On Sat, Apr 28, 2012 at 10:27 AM, John C Nash <nashjc at uottawa.ca> wrote:
> I've been creating some R tools that manipulate objective functions for
> optimization. In so doing, I create a character string with R code, and then
> want to have it in my workspace. Currently -- and this works fine -- I write
> the code out, then use source() to bring it in again. Example:
>
> cstr<-"jack<-function(x){\n cat(\"Silly x:\")\n print(x) \n  }\n"
> write(cstr, file='tfile.txt')
> jack<-source('tfile.txt')$value # You need the value element!
> print(jack)
>
> However, I feel it would be more elegant if I could avoid the file, and am
> sure I must have missed some way to pipe the cstr through the source()
> function. Also, if the file cannot be written (directory permissions?), then
> my approach won't work.

Try this:

> cstr<-"jack<-function(x){\n cat(\"Silly x:\")\n print(x) \n  }\n"
> eval(parse(text = cstr))
> jack(0)
Silly x:[1] 0

This also works:

> f <- function(x) {}
> body(f) <- parse(text = '{\n cat("Silly x:")\n print(x) \n  }\n')
> f("X")
Silly x:[1] "X"


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