[R] eval and as.name

[Wacek Kusnierczyk]

Murray Cooper wrote:
> I am new to R, so maybe I'm missing the point of your question. But
> why wouldn't you just use sum(a,b)?

if you know you want to sum a and b, sure you would.  if you need to sum
the variables named by the components of some dynamic character vector,
you need to lookup ('dereference') the names in some way.

vQ

>
> Murray M Cooper, Ph.D.
> Richland Statistics
> 9800 N 24th St
> Richland, MI, USA 49083
> Mail: richstat at earthlink.net
> ----- Original Message ----- From: "Fuchs Ira" <irafuchs at gmail.com>
> To: <r-help at r-project.org>
> Sent: Thursday, February 05, 2009 5:10 PM
> Subject: [R] eval and as.name
>
>
>> I'm sure there is a more general way to ask this question but how do 
>> you use the elements of a character vector as names of objects in an
>> expression?
>> For example, say you have:
>>
>> a = c(1,3,5,7)
>> b = c(2,4,6,8)
>>
>> n=c("a","b")
>>
>> and you want to use the names a and b in a function (e.g. sum)
>>
>> sum(eval(as.name(n[1])),eval(as.name(n[2])))
>>
>> works but
>>
>> what is a simpler way to effect this level of indirection?
>>
>> ______________________________________________
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>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.