[R] a question about function eval()

[Uwe Ligges]

Feng Chen wrote:

> Hi,
> 
> I have a question about the usage of eval(). Wonder if any experienced user can help me out of it.
> 
> I use eval() in the following function:
> semireg.pwl <- function(coef.s=rnorm(1),coef.a=rnorm(1),knots.pos=knots.x,knots.ini.val=knots.val){
>   knotn <- length(knots.pos)
>   def.par.env <- sys.frame(1)
>   print(def.par.env)
>   print(environment(coef.s))
>   tg <- eval( (parse(text=
>                      paste(
>                            "function(coef.sex=coef.s,coef.age=coef.a,",
>                            paste("knot.val.",1:knotn,"=knots.ini.val[",1:knotn,"]",sep="",collapse=","),
>                            ")",
>                            "{\n print(sys.frame());print(coef.sex)\n  y <- c(",
>                            paste("knot.val.",1:knotn,sep="",collapse=","),
>                            ")\n",
>                            "  -loglikelihood(coef.sex,coef.age,knots.pos,y)\n}",
>                            sep="",collapse=""
>                            )
>                      )
>                )
>              ,envir=def.par.env)

Why do you want to use eval(parse(.....))? That's not sensible in this 
case. You can either alculate the stuff doirectly or define a function 
instead....

Uwe Ligges



>   print(tg())
>   print(coef.s)
>   print(sys.frame(1))
>   mle(tg)
> }
> 
> But when I ran semireg.pwl(), I got correct value for tg(), but an message 
> "Error in eval(expr, envir, enclos) : Object "coef.s" not found" 
> for mle(tg). I just don't know how to make the environment variable visible for mle().
> 
> Thanks a lot!
> 
> Feng
> 	[[alternative HTML version deleted]]
> 
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