HI,
Try this:
my.data$item_Num<- ave(my.data[,1],my.data[,1],FUN=seq_along)
head(my.data)
# person item_Num
#1 1 1
#2 1 2
#3 1 3
#4 1 4
#5 2 1
#6 2 2
#or,
unlist(tapply(my.data[,1],my.data[,1],FUN=seq_along),use.names=FALSE)
# [1] 1 2 3 4 1 2 1 2 3 4 5 6 7 1 2 3
#or
unlist(sapply(split(my.data,my.data[,1]),function(x)
1:nrow(x)),use.names=FALSE)
# [1] 1 2 3 4 1 2 1 2 3 4 5 6 7 1 2 3
A.K.
----- Original Message -----
From: Paul Artes <paul_h_ar...@yahoo.co.uk>
To: r-help@r-project.org
Cc:
Sent: Tuesday, November 13, 2012 8:50 PM
Subject: [R] numbering observations: help please!
Dear Friends,
I have the very simple problem of needing to number observations in a data
frame. After scratching the rest of my hair off my head without inspiration,
I'm using a silly loop. I'm sure that there is a much more elegant and
faster solution - can anyone help?
Here is an example:
my.data <- data.frame (person=c(1,1,1,1,2,2,3,3,3,3,3,3,3,4,4,4)) # now I
want to number those observations sequentially
# for each person
my.data$item.number <- 0
for (i in 1:length(unique(my.data$person))) {
my.data$item.number [which (my.data$person == unique(my.data$person)[i])]
<- seq (1:dim(tmp)[1]) }
--
View this message in context:
http://r.789695.n4.nabble.com/numbering-observations-help-please-tp4649457.html
Sent from the R help mailing list archive at Nabble.com.
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
