person-level to person-period xfm

Dear R experts,

I have a so-called person-level data frame that I need to transform
into a person-period data frame.

If the lingo is unclear, the data have one row for each subject, with
repeated measures data each in a separate column.

I need to transform these data so that each subject has multiple rows,
one for each repeated measure value.

Is there a quick-and-dirty way to do this transformation?

Many thanks,

  

Robert Terwilliger wrote:

Dear R experts,

I have a so-called person-level data frame that I need to transform
into a person-period data frame.

If the lingo is unclear, the data have one row for each subject, with
repeated measures data each in a separate column.

I need to transform these data so that each subject has multiple  
rows,
one for each repeated measure value.

Is there a quick-and-dirty way to do this transformation?

Many thanks,

There are several ways.  This is one.

tmp <- data.frame(id=letters[1:3], x1=1:3, x2=4:6, x3=7:9, x4=10:12)
tmp

id x1 x2 x3 x4
1  a  1  4  7 10
2  b  2  5  8 11
3  c  3  6  9 12

reshape(tmp, direction="long", varying=list(names(tmp)[-1]),  

ids="id")
  id time x1
a.1  a    1  1
b.1  b    1  2
c.1  c    1  3
a.2  a    2  4
b.2  b    2  5
c.2  c    2  6
a.3  a    3  7
b.3  b    3  8
c.3  c    3  9
a.4  a    4 10
b.4  b    4 11
c.4  c    4 12