[R] from matrix to data.frame

[jim holtman]

the reshape package might also help:

> require(reshape)
> x
  A  B  C  D  E
1 1  6 11 16 21
2 2  7 12 17 22
3 3  8 13 18 23
4 4  9 14 19 24
5 5 10 15 20 25
> melt(t(x))
   X1 X2 value
1   A  1     1
2   B  1     6
3   C  1    11
4   D  1    16
5   E  1    21
6   A  2     2
7   B  2     7
8   C  2    12
9   D  2    17
10  E  2    22
11  A  3     3
12  B  3     8
13  C  3    13
14  D  3    18
15  E  3    23
16  A  4     4
17  B  4     9
18  C  4    14
19  D  4    19
20  E  4    24
21  A  5     5
22  B  5    10
23  C  5    15
24  D  5    20
25  E  5    25


On Tue, Jan 20, 2009 at 9:10 AM, Antje <niederlein-rstat at yahoo.de> wrote:
> Hello,
>
> I have a question how to reshape a given matrix to a data frame.
>
> # ----------------------------------
>> a <- matrix(1:25, nrow=5)
>> a
>     [,1] [,2] [,3] [,4] [,5]
> [1,]    1    6   11   16   21
> [2,]    2    7   12   17   22
> [3,]    3    8   13   18   23
> [4,]    4    9   14   19   24
> [5,]    5   10   15   20   25
>
>> colnames(a) <- LETTERS[1:5]
>> rownames(a) <- as.character(1:5)
>> a
>  A  B  C  D  E
> 1 1  6 11 16 21
> 2 2  7 12 17 22
> 3 3  8 13 18 23
> 4 4  9 14 19 24
> 5 5 10 15 20 25
>
> # -----------------------------------
>
> This is an example on how my matrix looks like.
> Now, I'd like to reshape the data that I get a data frame with three
> columns:
>
> - the row name of the enty (X1)
> - the column name of the entry (X2)
> - the entry itself (X3)
>
> like:
>
> X1      X2      X3
> 1       A       1
> 2       A       2
> 3       A       3
> ....
> 1       B       6
> 2       B       7
> ....
> 5       E       25
>
> How would you solve this problem in an elegant way?
>
> Antje
>
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?