# [R] Reshape matrix from wide to long format

stephen sefick ssefick at gmail.com
Tue Nov 25 14:07:07 CET 2008

```#handy if you like ggplot2 as this is required
#I think this is what you want
library(reshape)
m <- matrix(1:20, nrow=4, dimnames=list(LETTERS[1:4], letters[1:5]))
melt(m)

On Tue, Nov 25, 2008 at 8:01 AM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> Try this:
>
>> as.data.frame.table(m)
>   Var1 Var2 Freq
> 1     A    a    1
> 2     B    a    2
> 3     C    a    3
> 4     D    a    4
> 5     A    b    5
> 6     B    b    6
> 7     C    b    7
> 8     D    b    8
> 9     A    c    9
> 10    B    c   10
> 11    C    c   11
> 12    D    c   12
> 13    A    d   13
> 14    B    d   14
> 15    C    d   15
> 16    D    d   16
> 17    A    e   17
> 18    B    e   18
> 19    C    e   19
> 20    D    e   20
>
>
> On Tue, Nov 25, 2008 at 7:19 AM, Daren Tan <daren76 at hotmail.com> wrote:
>>
>>
>> I forgot the reshape equivalent for converting from wide to long format. Can someone help as my matrix is very big. The followin is just an example.
>>
>>> m <- matrix(1:20, nrow=4, dimnames=list(LETTERS[1:4], letters[1:5]))
>>> m
>>   a b c d e
>>  A 1 5 9 13 17
>>  B 2 6 10 14 18
>>  C 3 7 11 15 19
>>  D 4 8 12 16 20
>>
>>> as.data.frame(cbind(rep(rownames(m), ncol(m)), rep(colnames(m), each=nrow(m)), c(m)))
>>  V1 V2 V3
>>  1 A a 1
>>  2 B a 2
>>  3 C a 3
>>  4 D a 4
>>  5 A b 5
>>  6 B b 6
>>  7 C b 7
>>  8 D b 8
>>  9 A c 9
>> 10 B c 10
>> 11 C c 11
>> 12 D c 12
>> 13 A d 13
>> 14 B d 14
>> 15 C d 15
>> 16 D d 16
>> 17 A e 17
>> 18 B e 18
>> 19 C e 19
>> 20 D e 20
>>
>> ______________________________________________
>> 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.
>>
>
> ______________________________________________
> 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.
>

--
Stephen Sefick

Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods.  We are mammals, and have not exhausted the
annoying little problems of being mammals.

-K. Mullis

```