[R] Evaluating a string

[David Winsemius]

On Jul 2, 2010, at 2:05 AM, Joshua Wiley wrote:

> Hello Jonathan,
>
> You can use eval() and parse(), although there may be better ways of
> getting to your end goal


 > do.call(operator, list(a,b))
[1] 1


> (assuming you have not inherited a series of
> character strings held in objects that should be run as commands).  At
> any rate, this works:
>
> a <- 3
> b <- 2
> operator <- "-"
> statement_string <- paste(a, operator, b, sep="")
> eval(parse(text = statement_string))
>
> Best regards,
>
> Josh
>
>
> On Thu, Jul 1, 2010 at 2:54 PM, Jonathan Greenberg
> <greenberg at ucdavis.edu> wrote:
>> Rhelpers:
>>
>> How do I get R to evaluate a string, as if it was an R statement,  
>> e.g.:
>>
>> a=3
>> b=2
>> operator="-"
>> statement_string=paste(a,operator,b,sep="")
>>
>> --j


David Winsemius, MD
West Hartford, CT