R help - Jun 2012 - Indexing Grouped Data

I need help in indexing grouped data. In this excample (df1 data), the first
child had a first immunization at age 2. The second child had the first, second
and third immunization at age 5,10, and 12, the third child had first and second
immunization at age 4 and 6 and the fourth child had the first immunization at
age 2. I have df1 and I need to create df2 with and "ind' variable that
indicate if the immunization is first, second or third. Note that the data is
not balanced but is sorted such that the fisrt observation (of an individual) is
the first immunization. 
 
 
> df1 <- data.frame(id = c(1,2,2,2,3,3,4), age = c(4,5,10, 12, 4,6, 2),
dose = c(1.8,1.8,1.6,1.2,1.8,1.6,1.8))
>               
> df2 <- data.frame(id = c(1,2,2,2,3,3,4), age = c(4,5,10, 12, 4,6, 2),
ind=c(1,1,2,3,1,2,1), dose = c(1.8,1.8,1.6,1.2,1.8,1.6,1.8))
> 
> df1
  id age dose
1  1   4  1.8
2  2   5  1.8
3  2  10  1.6
4  2  12  1.2
5  3   4  1.8
6  3   6  1.6
7  4   2  1.8
> df2
  id age ind dose
1  1   4   1  1.8
2  2   5   1  1.8
3  2  10   2  1.6
4  2  12   3  1.2
5  3   4   1  1.8
6  3   6   2  1.6
7  4   2   1  1.8
> 

Peter Maclean
Department of Economics
UDSM
	[[alternative HTML version deleted]]

df1$ind <- ave(integer(nrow(df1)), df1$id, FUN=seq_along)

There are faster ways to do this if you know that id is sorted.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org] On Behalf
> Of Peter Maclean
> Sent: Wednesday, June 13, 2012 7:15 AM
> To: R mailing list
> Subject: Re: [R] Indexing Grouped Data
> 
> I need help in indexing grouped data. In this excample (df1 data), the
first child had a
> first?immunization at age 2. The second child had the first, second and
third immunization
> at age 5,10, and 12, the third child had first and second immunization at
age 4 and 6 and
> the fourth child had the first immunization at age 2.?I have df1 and I need
to create df2
> with and "ind' variable that indicate if the immunization is
first, second or third. Note that
> the data is not balanced but is sorted such that the fisrt observation (of
an individual) is
> the first immunization.
> 
> 
> > df1 <- data.frame(id = c(1,2,2,2,3,3,4), age = c(4,5,10, 12, 4,6,
2), dose > c(1.8,1.8,1.6,1.2,1.8,1.6,1.8))
> >
> > df2 <- data.frame(id = c(1,2,2,2,3,3,4), age = c(4,5,10, 12, 4,6,
2), ind=c(1,1,2,3,1,2,1),
> dose = c(1.8,1.8,1.6,1.2,1.8,1.6,1.8))
> >
> > df1
> ? id age dose
> 1? 1?? 4? 1.8
> 2? 2?? 5? 1.8
> 3? 2? 10? 1.6
> 4? 2? 12? 1.2
> 5? 3?? 4? 1.8
> 6? 3?? 6? 1.6
> 7? 4?? 2? 1.8
> > df2
> ? id age ind dose
> 1? 1?? 4?? 1? 1.8
> 2? 2?? 5?? 1? 1.8
> 3? 2? 10?? 2? 1.6
> 4? 2? 12?? 3? 1.2
> 5? 3?? 4?? 1? 1.8
> 6? 3?? 6?? 2? 1.6
> 7? 4?? 2?? 1? 1.8
> >
> 
> 
> Peter Maclean
> Department of Economics
> UDSM
> 	[[alternative HTML version deleted]]