Hi Daniel,
> I am correcting you. :-) You are using dim() incorrectly, and not accessing
>the array correctly.
>
> In all of your examples you should be using dim(3,4,2). Then you need to
>specify the indexes
>
> of the array element you want to look at. So, to use your example
Thanks for your correction. So the index to be used in my example should be
(3,4,2) only.
But still I'm not very clear re your advice on follows
> a<-1:24
> a3d <- array(a, dim = c(3,4,2))
> a3d
, , 1
[,1] [,2] [,3] [,4]
[1,] 1 4 7 10
[2,] 2 5 8 11
[3,] 3 6 9 12
, , 2
[,1] [,2] [,3] [,4]
[1,] 13 16 19 22
[2,] 14 17 20 23
[3,] 15 18 21 24
>
> # 1 maps to a[1, 1, 1] in the 3d array
> a3d[1, 1, 1]
[1] 1
>
> # 2 maps to a[2, 1, 1].
> a3d[2, 1, 1]
[1] 2
>
> # 3 maps to a[3, 1, 1]
> a3d[3, 1, 1]
[1] 3
>
> # 4 maps to a[1, 2, 1]
> a3d[1, 2, 1]
[1] 4
What does it mean;
[1] 1
[1] 2
[1] 3
[1] 4
as mentioned ?
Anyway I'll move/continue on the manual to see what will happen.
B.R.
Stephen L
----- Original Message ----
From: Daniel Nordlund <djnordl...@frontier.com>
To: r-help@r-project.org
Sent: Sun, November 7, 2010 2:08:04 AM
Subject: Re: [R] About 5.1 Arrays
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
> On Behalf Of Stephen Liu
> Sent: Saturday, November 06, 2010 7:38 AM
> To: Joshua Wiley
> Cc: r-help@r-project.org
> Subject: Re: [R] About 5.1 Arrays
>
> Hi Joshua,
>
> Thanks for your advice.
>
> 1)
> Re your advice:-[quote]
> > a3d
> , , 1 <--- this is the first position of the third dimension
>
> [,1] [,2] [,3] [,4] <--- positions 1, 2, 3, 4 of the second
> dimension
> [1,] 1 4 7 10
> [2,] 2 5 8 11
> [3,] 3 6 9 12
> ^ the first dimension
>
> , , 2 <--- the second position of the third dimension
> ...
> [/quote]
>
> Where is the third dimension?
>
>
> 2)
> Re your advice:-[quote]
> so you can think that in the original vector "a":
> 1 maps to a[1, 1, 1] in the 3d array
> 2 maps to a[2, 1, 1].
> 3 maps to a[3, 1, 1]
> 4 maps to a[1, 2, 1]
> 12 maps to a[3, 4, 1]
> 20 maps to a[2, 3, 2]
> 24 maps to a[3, 4, 2]
> [/quote]
>
> My finding;
>
> # 1 maps to a[1, 1, 1] in the 3d array
> > a3d <- array(a, dim = c(1, 1, 1))
> > a3d
> , , 1
>
> [,1]
> [1,] 1
>
> Correct
>
> # 2 maps to a[2, 1, 1].
> > a3d <- array(a, dim = c(2, 1, 1))
> > a3d
> , , 1
>
> [,1]
> [1,] 1
> [2,] 2
>
> Correct
>
> # 3 maps to a[3, 1, 1]
> > a3d <- array(a, dim = c(3, 1, 1))
> > a3d
> , , 1
>
> [,1]
> [1,] 1
> [2,] 2
> [3,] 3
>
> Correct
>
> # 4 maps to a[1, 2, 1]
> > a3d <- array(a, dim = c(1, 2, 1))
> > a3d
> , , 1
>
> [,1] [,2]
> [1,] 1 2
>
> Incorrect. It is "2"
>
>
> # 12 maps to a[3, 4, 1]
> > a3d <- array(a, dim = c(3, 4, 1))
> > a3d
> , , 1
>
> [,1] [,2] [,3] [,4]
> [1,] 1 4 7 10
> [2,] 2 5 8 11
> [3,] 3 6 9 12
>
> Correct
>
> # 20 maps to a[2, 3, 2]
> > a3d <- array(a, dim = c(2, 3, 2))
> > a3d
> , , 1
>
> [,1] [,2] [,3]
> [1,] 1 3 5
> [2,] 2 4 6
>
> , , 2
>
> [,1] [,2] [,3]
> [1,] 7 9 11
> [2,] 8 10 12
>
> Incorrect. It is "12"
>
>
> # 24 maps to a[3, 4, 2]
> > a3d <- array(a, dim = c(3, 4, 2))
> > a3d
> , , 1
>
> [,1] [,2] [,3] [,4]
> [1,] 1 4 7 10
> [2,] 2 5 8 11
> [3,] 3 6 9 12
>
> , , 2
>
> [,1] [,2] [,3] [,4]
> [1,] 13 16 19 22
> [2,] 14 17 20 23
> [3,] 15 18 21 24
>
> Correct.
>
> If I'm wrong, pls correct me. Thanks
>
>
> B.R.
> Stephen
>
Stephen,
I am correcting you. :-) You are using dim() incorrectly, and not accessing
the
array correctly. In all of your examples you should be using dim(3,4,2). Then
you need to specify the indexes of the array element you want to look at. So,
to
use your example
> a<-1:24
> a3d <- array(a, dim = c(3,4,2))
> a3d
, , 1
[,1] [,2] [,3] [,4]
[1,] 1 4 7 10
[2,] 2 5 8 11
[3,] 3 6 9 12
, , 2
[,1] [,2] [,3] [,4]
[1,] 13 16 19 22
[2,] 14 17 20 23
[3,] 15 18 21 24
>
> # 1 maps to a[1, 1, 1] in the 3d array
> a3d[1, 1, 1]
[1] 1
>
> # 2 maps to a[2, 1, 1].
> a3d[2, 1, 1]
[1] 2
>
> # 3 maps to a[3, 1, 1]
> a3d[3, 1, 1]
[1] 3
>
> # 4 maps to a[1, 2, 1]
> a3d[1, 2, 1]
[1] 4
Hope this is helpful,
Dan
Daniel Nordlund
Bothell, WA USA
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