Re: [R] Basic Question on Keys/Values

From: Douglas Bates <bates_at_stat.wisc.edu>
Date: Mon, 09 Jun 2008 13:33:19 -0500

On Mon, Jun 9, 2008 at 1:11 PM, Dumblauskas, Jerry <jerry.dumblauskas_at_credit-suisse.com> wrote:
> I've received a couple of responses telling me to use list (I was trying
> to use 2 equal length vectors but having an issue pulling out the index
> subscript).

Should you ever need to do that for another application, check

?which

> I can use lists now, and stop thrashing.... :)

> Thx again for the assistance!
>
> -----Original Message-----
> From: dmbates_at_gmail.com [mailto:dmbates_at_gmail.com] On Behalf Of Douglas
> Bates
> Sent: Monday, June 09, 2008 1:08 PM
> To: Dumblauskas, Jerry
> Cc: r-help_at_r-project.org
> Subject: Re: [R] Basic Question on Keys/Values
>
> On Mon, Jun 9, 2008 at 12:55 PM, Dumblauskas, Jerry
> <jerry.dumblauskas_at_credit-suisse.com> wrote:
>> As a java programmer, I'm having issue conceptualizing the following
>> use
>> case:

>
>> Given an value, passed into a function, how do I pull out the lookup?

>
>> Ie.
>> A list of keys (key1, key2, key3)
>> A list of values (val1,val2,val3)

>
>> I want to write a function (or is there something built in?) such that
>
>> Callit <- (thekey) {
>> (magic happens here)
>> Return value
>> }
>
> If the keys are text strings then you can use a named list as the
> container.
>
>> foo <- list(a = 1:10, b = LETTERS[1:3], ttt = Formaldehyde) foo$b
> [1] "A" "B" "C"
>> bar <- "a"
>> foo$bar
> NULL
>> foo[[bar]]
> [1] 1 2 3 4 5 6 7 8 9 10
>
> Note that the $ operator is an extractor for an explicit name. If you
> want the value corresponding to a key which is itself stored as an
> object in R you must use the '[[' notation.
>
> Lists are suitable for a small to moderate number of key/value pairs.
> For large numbers of key/value pairs you may want to consider
> environments instead.
>
>> Any ideas?
>>
>> Thanks a bunch!
>>
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>
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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. Received on Mon 09 Jun 2008 - 18:55:16 GMT

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