Convert subsets of a column to new dataframe rows in R

Question

I would like to turn a dataframe column with unique identifiers into multiple rows (one row for each unique identifier)

Example:

V1    V2    Unique
5     12      1
10    15      1
20    35      1
40    50      2
60    70      2
100   50      2

What I need is:

row1 5 10 20
row2 40 60 100

Essentially I would like a row of V1 (ordering from left to right for first to last match) when Unique is the same (ignoring V2 entirely)

Thanks in advance.

are those always of same length? ie 3 in this case? otherwise you would be adding extra columns..or may be you want list or vector id that is of different length? — Ananta, Feb 04 '14 at 23:20

score 1 · Accepted Answer · answered Feb 04 '14 at 23:23

1

For example using unstack , if all groups have the same length:

t(unstack(dat[,c('V1','Unique')]))
   [,1] [,2] [,3]
X1    5   10   20
X2   40   60  100

Or if they don't have the same length, you can use split:

split(dat$V1,dat$Unique)
$`1`
[1]   5  10  20 100

$`2`
[1] 40 60

answered Feb 04 '14 at 23:23

agstudy

Works. They may or may not be the same length so this is great for either case. Thanks! – user3272284 Feb 04 '14 at 23:37

1 Answers1