[R] Eval() or parse() do not work inside function

[Joshua Wiley]

Dear Jorge,

It might help if you included some sample data that replicates your
problem, or, perhaps, the results of sessionInfo().  I cannot
replicate it.  Here are my results:


> data <- data.frame(A = 1:10, RECORD = 1:10)
>
> f.graph.two.vbs<-function(dataname,v1){
+   val<-paste(dataname,v1,sep="$")
+   val<-eval(parse(text=val))
+   val
+ }
>
> f.graph.two.vbs("data","RECORD")
 [1]  1  2  3  4  5  6  7  8  9 10
>

Everything seems to work as expected.  I am using:

> sessionInfo()
R version 2.11.1 (2010-05-31)
x86_64-pc-mingw32

Josh

On Tue, Jul 27, 2010 at 11:34 AM, Jorge A. Ahumada
<j.ahumada at conservation.org> wrote:
> I am writing a function where the arguments are names of objects or variable
> names in a data frame. To convert the strings to the objects I am using
> eval(parse(text=name)):
>
> f.graph.two.vbs<-function(dataname,v1){
>
>     val<-paste(dataname,v1,sep="$")
>     val<-eval(parse(text=val))
>     val
>    }
>
> However running this returns an error:
>
>>f.graph.two.vbs("data","RECORD")
> Error in data$RECORD : $ operator is invalid for atomic vectors
>
> Repeating the individual commands in the workspace does work though.. Do I
> need to pass the object data in the arguments for this to work?
>
> Thanks,
>
> Jorge
> --
> Jorge A. Ahumada
> Technical Director
> Tropical Ecology Assessment and Monitoring Network (TEAM)
> Science and Knowledge Division
> Conservation International
> 2011 Crystal Dr. Suite 500
> Arlington, VA 22202
> Phone: 703-341-2543
> Mobile: 202-716-3374
> http://www.teamnetwork.org/
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/