[R] transfer string to expression

[Bert Gunter]

If it's not already clear, perhaps this slight variation might help
explain what's happening:

b0<-1
b1<-1
x<-1
str2expr<-function(y){eval(parse(text=y))}  ## Note change from "x" to "y" here
test1<-"b0+b1*sqrt(x)"
str2expr(test1)

Cheers,
Bert

On Sun, Oct 31, 2010 at 1:58 PM, Duncan Murdoch
<murdoch.duncan at gmail.com> wrote:
> On 31/10/2010 4:47 PM, Wu Gong wrote:
>>
>> Hi Duncan:
>>
>> I'm curious about the environment setting. ?eval says:
>>
>> "If envir is not specified, then the default is parent.frame() (the
>> environment where the call to eval was made). "
>>
>> So what's the difference between set envir=parent.frame() or not?
>
> If you pass parent.frame() as an argument, it will be one level up: it's the
> parent of the function that calls eval.  If you leave it at the default,
> it's the parent of eval, i.e. the function that calls it.
>
> Duncan Murdoch
>
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-- 
Bert Gunter
Genentech Nonclinical Biostatistics