[R] resizing data

arun smartpink111 at yahoo.com
Fri Jan 25 23:28:49 CET 2013

```HI,

It's not clear why you wanted to take the transpose and resize it afterwards.
It could be done in one step as David suggested.

Suppose, you wanted to get the result after you transposed the matrix:
x<-matrix(1:64,8)
x1<-t(x)

matrix(unlist(split(x1,row(x1))),ncol=4,byrow=T)
#      [,1] [,2] [,3] [,4]
#[1,]    1    2    3    4
#[2,]    5    6    7    8
#[3,]    9   10   11   12
#[4,]   13   14   15   16
-----------------------------
#or
do.call(rbind,lapply(split(x1,row(x1)),function(x) matrix(x,nrow=2,ncol=4,byrow=T)))
#  [,1] [,2] [,3] [,4]
#[1,]    1    2    3    4
#[2,]    5    6    7    8
#[3,]    9   10   11   12
#[4,]   13   14   15   16
--------------------------
A.K.

----- Original Message -----
From: emorway <emorway at usgs.gov>
To: r-help at r-project.org
Cc:
Sent: Friday, January 25, 2013 4:12 PM
Subject: [R] resizing data

Undoubtedly this question has been asked before, I just can't seem to find
the combination of search terms to produce it.  I'm trying to resize a
dataset that is pulled into R using read.table.  However, I think the same
problem can be produced using matrix:

x<-matrix(1:64,8)
x
#     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#[1,]    1    9   17   25   33   41   49   57
#[2,]    2   10   18   26   34   42   50   58
#[3,]    3   11   19   27   35   43   51   59
#[4,]    4   12   20   28   36   44   52   60
#[5,]    5   13   21   29   37   45   53   61
#[6,]    6   14   22   30   38   46   54   62
#[7,]    7   15   23   31   39   47   55   63
#[8,]    8   16   24   32   40   48   56   64

The true order of data in the larger problem I'm working with is actually
transposed, like so:
x<-t(x)
x
#     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#[1,]    1    2    3    4    5    6    7    8
#[2,]    9   10   11   12   13   14   15   16
#[3,]   17   18   19   20   21   22   23   24
#[4,]   25   26   27   28   29   30   31   32
#[5,]   33   34   35   36   37   38   39   40
#[6,]   41   42   43   44   45   46   47   48
#[7,]   49   50   51   52   53   54   55   56
#[8,]   57   58   59   60   61   62   63   64

I'm trying to resize the data (in this example, a matrix) to say a 16 x 4
matrix while preserving the consecutive order of the individual elements in
a left-to-right top-to-bottom fashion.  The example below is wrong because
the first row should be "1 2 3 4", how can I make this happen?  It would
also be nice to make a 4 x 16 matrix where the first row contains the values
of x[1,1:8] followed by x[2,1:8].  I'm guessing there is a 1 liner of R code
for this type of thing so I don't have to resort to nested for loops?

y<-matrix(x,nrow=16,ncol=4)
y
#      [,1] [,2] [,3] [,4]
# [1,]    1    3    5    7
# [2,]    9   11   13   15
# [3,]   17   19   21   23
# [4,]   25   27   29   31
# [5,]   33   35   37   39
# [6,]   41   43   45   47
# [7,]   49   51   53   55
# [8,]   57   59   61   63
# [9,]    2    4    6    8
#[10,]   10   12   14   16
#[11,]   18   20   22   24
#[12,]   26   28   30   32
#[13,]   34   36   38   40
#[14,]   42   44   46   48
#[15,]   50   52   54   56
#[16,]   58   60   62   64

--
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