Hi,
Assuming that there are two columns in your data.
dat1<-read.table(text="
ID Visit
x a1
x a2
y b1
y c23
y b33
",sep="",header=TRUE,stringsAsFactors=FALSE)
cnt<-count(dat1$ID)
colnames(cnt)<-c("ID","response")
merge(dat1,cnt,by="ID",all=TRUE)
# ID Visit response
#1 x a1 2
#2 x a2 2
#3 y b1 3
#4 y c23 3
#5 y b33 3
But, if there is only column and you want to split it
ID<-c("xa1","xa2","yb1","yc23","yb33")
ID1<-gsub("(.*)a.*|b.*|c.*","\\1",ID)
visit<-gsub(".*(a.*|b.*|c.*)","\\1",ID)
dat2<-data.frame(ID1,visit)
dat2[]<-lapply(dat2,as.character)
cnt<-count(dat2$ID1)
colnames(cnt)<-c("ID1","response")
merge(dat2,cnt,by="ID1",all=TRUE)
# ID1 visit response
#1 x a1 2
#2 x a2 2
#3 y b1 3
#4 y c23 3
#5 y b33 3
A.K.
----- Original Message -----
From: farnoosh sheikhi <farnoosh...@yahoo.com>
To: "r-help@R-project.org" <r-help@r-project.org>
Cc:
Sent: Tuesday, October 23, 2012 3:14 PM
Subject: [R] frequency
Hello,
I have a data as follow:
ID Visit
xa1
xa2
yb1
yc23
yb33
I want to look at frequency of visit for ID and create a new column as response
.
For example my response would be 2 for x and 3 for y.
I think I need to write a loop, but I don't know how.
I really appreciate your help.
Thanks a lot.
Best,Farnoosh Sheikhi
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