[R] Problem at subsetting matrix by using dimnames

[Agustin Lobo]

Thanks a lot.
Based on your suggestions, would the following
diag(mitest[c("a", "b", "c"), c("b", "c", "b")])

work in general? (it does for my example).
If so, I would prefer this form as I understand it better.

Agus



Henrique Dallazuanna wrote:
> Try this:
> 
> mapply(function(x, y)mitest[x, y], c("a", "b", "c"), c("b", "c", "b"))
> 
> or
> 
> diag(`[`(mitest, i = c("a", "b", "c"), j = c("b", "c", "b")))
> 
> 
> 
> On Wed, Sep 2, 2009 at 6:57 AM, Agustin Lobo <aloboaleu at gmail.com 
> <mailto:aloboaleu at gmail.com>> wrote:
> 
>     Given:
> 
>      > mitest <- matrix(1:16,ncol=4)
>      > dimnames(mitest)[[1]] <- c("a","b","c","d")
>      > dimnames(mitest)[[2]] <- c("a","b","c","d")
>      > mitest
>      a b  c  d
>     a 1 5  9 13
>     b 2 6 10 14
>     c 3 7 11 15
>     d 4 8 12 16
> 
>     I can do:
>      > mitest[cbind(c(1,2,3),c(2,3,2))]
>     [1]  5 10  7
> 
>     but using the names does not work:
>      > mitest[cbind(c("a","b","c"),c("b","c","b"))]
>     [1] NA NA NA NA NA NA
> 
>     despite the fact that
>      > mitest["a","b"]
>     [1] 5
> 
>     works fine.
> 
>     How can I do the equivalent of
>      > mitest[cbind(c(1,2,3),c(2,3,2))]
> 
>     using row and column names?
> 
>     Thanks
> 
>     Agus
> 
> 
>     -- 
>     Dr. Agustin Lobo
>     Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
>     LLuis Sole Sabaris s/n
>     08028 Barcelona
>     Spain
>     Tel. 34 934095410
>     Fax. 34 934110012
>     email: Agustin.Lobo at ija.csic.es <mailto:Agustin.Lobo at ija.csic.es>
>     http://www.ija.csic.es/gt/obster
> 
>     ______________________________________________
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> 
> 
> 
> 
> -- 
> Henrique Dallazuanna
> Curitiba-Paraná-Brasil
> 25° 25' 40" S 49° 16' 22" O

-- 
Dr. Agustin Lobo
Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
LLuis Sole Sabaris s/n
08028 Barcelona
Spain
Tel. 34 934095410
Fax. 34 934110012
email: Agustin.Lobo at ija.csic.es
http://www.ija.csic.es/gt/obster