[R] dataframe layout

[Gavin Simpson]

On Wed, 2007-03-14 at 03:53 -0500, Robert Baer wrote:
> Can someone remind me how to change the columns in df.a into a two column 
> df.b that contains one column of data and another column of the original 
> column headings as levels.
> 
> Example:
> a=1:3
> b=4:6
> c=7:9
> df.a=data.frame(a,b,c)
> 
> Should become in df.b:
> dat   lev
> 1      a
> 2      a
> 3      a
> 4      b
> 5      b
> 6      b
> 7      c
> 8      c
> 9      c
> 
> Thanks.

One option is stack()

> a=1:3
> b=4:6
> c=7:9
> df.a=data.frame(a,b,c)
> df.a
  a b c
1 1 4 7
2 2 5 8
3 3 6 9
> stack(df.a)
  values ind
1      1   a
2      2   a
3      3   a
4      4   b
5      5   b
6      6   b
7      7   c
8      8   c
9      9   c
> class(stack(df.a))
[1] "data.frame"

HTH

G

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Gavin Simpson                     [t] +44 (0)20 7679 0522
ECRC                              [f] +44 (0)20 7679 0565
UCL Department of Geography
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