[R] Simplest question ever...

[(Ted Harding)]

On 01-Mar-07 Paul Lynch wrote:
> I'm not sure this is the most efficient, but how about:
>    diag(m[a,b])
> ?

m[cbind(a,b)] will also do it:

m
     [,1] [,2] [,3] [,4] [,5] [,6] [,7]
[1,]  1.1  1.2  1.3  1.4  1.5  1.6  1.7
[2,]  2.1  2.2  2.3  2.4  2.5  2.6  2.7
[3,]  3.1  3.2  3.3  3.4  3.5  3.6  3.7
[4,]  4.1  4.2  4.3  4.4  4.5  4.6  4.7
[5,]  5.1  5.2  5.3  5.4  5.5  5.6  5.7

a <- c(1, 4, 5)
b <- c(2, 6, 7)

diag(m[a,b])
[1] 1.2 4.6 5.7

m[cbind(a,b)]
[1] 1.2 4.6 5.7

Ted.

> On 3/1/07, yoooooo <magno_yu at ml.com> wrote:
>>
>> Let's say i have
>>
>> a = c(1, 4, 5)
>> b = c(2, 6, 7)
>>
>> and i have matrix m, what's an efficient way of access
>> m[1, 2], m[4, 6], m[5, 7]
>> like of course m[a, b] = is not going to do, but what's an expression
>> that
>> will allow me to have that list?
>>
>> Thanks!
>> --
>> View this message in context:
>> http://www.nabble.com/Simplest-question-ever...-tf3329894.html#a9258932
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
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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.
>>
> 
> ______________________________________________
> R-help at stat.math.ethz.ch 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.

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Date: 01-Mar-07                                       Time: 23:44:22
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