[R] Using a number as a name to access a list

[Dimitris Rizopoulos]

lists are like vectors, i.e.,

x <- c("a" = 1, "b" = 2)
path <- "b"
x[path]

the same applies to lists:

lis <- list(a = 1:3)
path <- "a"
lis[path]

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "michael watson (IAH-C)" <michael.watson at bbsrc.ac.uk>
To: <r-help at stat.math.ethz.ch>
Sent: Thursday, February 10, 2005 2:35 PM
Subject: [R] Using a number as a name to access a list


> Hi
>
> Dumb question time again, for which I apologise.
>
> I have a variable that contains the following numerical text 
> "04010".
> This is the name to access a list:
>
>> as.list(KEGGPATHID2NAME)$"04010"
> [1] "MAPK signaling pathway"
>
> Marvellous!  Except I want to do that when "04010" is assigned to a
> variable called path and I can't figure out how to do it!
>
>> path <- "04010"
>>
>> # the original and best
>> as.list(KEGGPATHID2NAME)$"04010"
> [1] "MAPK signaling pathway"
>>
>> # clearly this doesn't, and shouldn't, work
>> as.list(KEGGPATHID2NAME)$path
> NULL
>>
>> # this produces a string...
>> eval(paste("as.list(KEGGPATHID2NAME)$",path,sep=''))
> [1] "as.list(KEGGPATHID2NAME)$04010"
>>
>> # as does this
>> eval(paste('as.list(KEGGPATHID2NAME)$"',path,'"',sep=''))
> [1] "as.list(KEGGPATHID2NAME)$\"04010\""
>>
>
> Whats really annoying is that when everyone mails me the answer, I'm
> going to have known how obvious it is.... Thanks in advance
>
> Mick
> Village Idiot
>
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