R help - Oct 2009 - Get subset of n dimensional matrix

I want to select a subset of an array, but I want to make a function so that
it can handle any number of dimensions.

This is probably best described with an example
> x <- 1:100
> dim(x) <- c(10,10)
> x
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    1   11   21   31   41   51   61   71   81    91
 [2,]    2   12   22   32   42   52   62   72   82    92
 [3,]    3   13   23   33   43   53   63   73   83    93
 [4,]    4   14   24   34   44   54   64   74   84    94
 [5,]    5   15   25   35   45   55   65   75   85    95
 [6,]    6   16   26   36   46   56   66   76   86    96
 [7,]    7   17   27   37   47   57   67   77   87    97
 [8,]    8   18   28   38   48   58   68   78   88    98
 [9,]    9   19   29   39   49   59   69   79   89    99
[10,]   10   20   30   40   50   60   70   80   90   100
>
> vList <- vector("list", 2)
> vList[[1]] <- c(4:6)
> vList[[2]] <- c(4:6)
> x[vList[[1]],vList[[2]]]
     [,1] [,2] [,3]
[1,]   34   44   54
[2,]   35   45   55
[3,]   36   46   56

but if:
> x <- 1:1000
> dim(x) <- c(10,10,10)
I would would have to increase the returning call:
x[vList[[1]],vList[[2]],vList[[3]]]

What I would like to be able to do is pass x the list of lists and have it
return the required points.

Anyone have any clues on how to get over this hurdle?

Thank you

Mark

	[[alternative HTML version deleted]]

Try this:

x <- array(1:1000, rep(10, 3))
vList <- list(i = 4:6, j = 4:6, ... = 4:6)
do.call('[', c(list(x), vList))

On Fri, Oct 9, 2009 at 7:18 AM, Mark McDowall
<markmcdowall1 at googlemail.com> wrote:
> I want to select a subset of an array, but I want to make a function so
that
> it can handle any number of dimensions.
>
> This is probably best described with an example
>
>> x <- 1:100
>> dim(x) <- c(10,10)
>> x
> ? ? ?[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
> ?[1,] ? ?1 ? 11 ? 21 ? 31 ? 41 ? 51 ? 61 ? 71 ? 81 ? ?91
> ?[2,] ? ?2 ? 12 ? 22 ? 32 ? 42 ? 52 ? 62 ? 72 ? 82 ? ?92
> ?[3,] ? ?3 ? 13 ? 23 ? 33 ? 43 ? 53 ? 63 ? 73 ? 83 ? ?93
> ?[4,] ? ?4 ? 14 ? 24 ? 34 ? 44 ? 54 ? 64 ? 74 ? 84 ? ?94
> ?[5,] ? ?5 ? 15 ? 25 ? 35 ? 45 ? 55 ? 65 ? 75 ? 85 ? ?95
> ?[6,] ? ?6 ? 16 ? 26 ? 36 ? 46 ? 56 ? 66 ? 76 ? 86 ? ?96
> ?[7,] ? ?7 ? 17 ? 27 ? 37 ? 47 ? 57 ? 67 ? 77 ? 87 ? ?97
> ?[8,] ? ?8 ? 18 ? 28 ? 38 ? 48 ? 58 ? 68 ? 78 ? 88 ? ?98
> ?[9,] ? ?9 ? 19 ? 29 ? 39 ? 49 ? 59 ? 69 ? 79 ? 89 ? ?99
> [10,] ? 10 ? 20 ? 30 ? 40 ? 50 ? 60 ? 70 ? 80 ? 90 ? 100
>>
>> vList <- vector("list", 2)
>> vList[[1]] <- c(4:6)
>> vList[[2]] <- c(4:6)
>> x[vList[[1]],vList[[2]]]
> ? ? [,1] [,2] [,3]
> [1,] ? 34 ? 44 ? 54
> [2,] ? 35 ? 45 ? 55
> [3,] ? 36 ? 46 ? 56
>
> but if:
>
>> x <- 1:1000
>> dim(x) <- c(10,10,10)
>
> I would would have to increase the returning call:
> x[vList[[1]],vList[[2]],vList[[3]]]
>
> What I would like to be able to do is pass x the list of lists and have it
> return the required points.
>
> Anyone have any clues on how to get over this hurdle?
>
> Thank you
>
> Mark
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org 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.
>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O