Re: [R] unquoting

From: Murray Jorgensen <maj_at_stats.waikato.ac.nz>
Date: Mon 21 Aug 2006 - 07:26:38 EST

Thank you, Brian, Peter and Gabor

Brian has what want. My heading was a bit misleading. I was looking for a function that would, in logicians' terms, convert 'mention' into 'use'. (This usually goes along with the story about the importance of knowing the difference between a lion and "lion".) get() is just such a function.

Murray Jorgensen

Prof Brian Ripley wrote:

> ?get
> 
> I really think this has nothing to do with `quoting', rather to do with 
> evaluating variables from their names. At first I though you were looking 
> for noquote(), which does unquote in the conventional sense.
> 

>> noquote(names(AF)[2])
> [1] Second

>> get(names(AF)[2])
> [1] 3 4
> 
> On Sun, 20 Aug 2006, Murray Jorgensen wrote:
> 

>> I would like a function to strip quotes off character strings. I should
>> work like this:
>>
>> > A <- matrix(1:6, nrow = 2, ncol=3)
>> > AF <- as.data.frame(A)
>> > names(AF) <- c("First","Second","Third")
>> > AF
>> First Second Third
>> 1 1 3 5
>> 2 2 4 6
>> > names(AF)[2]
>> [1] "Second"
>> > attach(AF)
>> > unquote(names(AF)[2])
>> [1] 3 4
>>
>> Of course what I actually get is
>>
>> Error: couldn't find function "unquote"
>>
>> The reason that I want to do this is that I have a frame with a rather
>> large number of variables and I would like to loop over the names and
>> print out various descriptive summaries of the variable's distribution.
>>
>> OK, OK, I could just go
>>
>> > AF[,2]
>> [1] 3 4
>>
>> but once I thought of unquoting I have some sort of inner need to know
>> how to do it!
>>
>> Cheers,
>>
>> Murray
>>
>
-- 
Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
Department of Statistics, University of Waikato, Hamilton, New Zealand
Email: maj@waikato.ac.nz                                Fax 7 838 4155
Phone  +64 7 838 4773 wk    Home +64 7 825 0441    Mobile 021 1395 862

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Received on Mon Aug 21 07:33:52 2006

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