[R] reshape data.frame

[Dennis Murphy]

This is very straightforward using the reshape2 package:

library('reshape2')
dc <- dcast(a, name ~ year, value_var = 'amount')

  name 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
1    a    1    2    3    4    5    6    7    8    9   10   NA   NA   NA   NA
2    b   11   12   13   14   15   16   17   18   19   20   21   22   23   24
  1985
1   NA
2   25

dcast() returns a data frame; a companion function acast() returns a
matrix. If you want to change the names afterward, use

names(dc)[-1] <- paste('X', 1971:1985, sep = '.')

HTH,
Dennis

On Fri, Nov 18, 2011 at 4:04 PM, Trevor Davies <davies.trevor at gmail.com> wrote:
> A late friday afternoon coding question.  I'm having a hard time thinking
> of the correct search terms for what I want to do.
>
> If I have a df like this:
>
>  a <-
> data.frame(name=c(rep('a',10),rep('b',15)),year=c(1971:1980,1971:1985),amount=1:25)
>   name year amount
> 1     a 1971      1
> 2     a 1972      2
> 3     a 1973      3
> 4     a 1974      4
> 5     a 1975      5
> 6     a 1976      6
> 7     a 1977      7
> 8     a 1978      8
> 9     a 1979      9
> 10    a 1980     10
> 11    b 1971     11
> 12    b 1972     12
> 13    b 1973     13
> 14    b 1974     14
> 15    b 1975     15
> 16    b 1976     16
> 17    b 1977     17
> 18    b 1978     18
> 19    b 1979     19
> 20    b 1980     20
> 21    b 1981     21
> 22    b 1982     22
> 23    b 1983     23
> 24    b 1984     24
> 25    b 1985     25
>
>
> and I'd like to reshape it so it is like this:
>  X.1971 X.1972 X.1973 X.1974 X.1975 X.1976 X.1977 X.1978 X.1979 X.1980
> X.1981
> a      1      2      3      4      5      6      7      8      9     10
> NA
> b     11     12     13     14     15     16     17     18     19     20
> 21
>  X.1982 X.1983 X.1984 X.1985
> a     NA     NA     NA     NA
> b     22     23     24     25
>
> Thanks for the assist.
>
>        [[alternative HTML version deleted]]
>
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