Hi, May be this helps: dat1<- read.table(text=" pbnr dat dep dys sop ago mis age female 1 10023 1994-02-21 0.75 1.00 0.50 0.50 0.75 35 1 2 10023 1994-05-25 0.75 1.00 0.50 0.50 0.75 35 1 3 10028 1994-02-01 2.00 1.75 3.00 0.50 1.50 42 1 4 10028 1999-01-15 1.25 0.75 2.25 0.50 0.25 42 1 5 10053 1994-03-16 2.50 0.75 1.25 0.50 1.25 22 1 6 10053 1994-09-23 3.25 1.25 1.25 0.75 2.25 22 1 ",sep="",header=TRUE,stringsAsFactors=FALSE) dat1$dat<- as.Date(dat1$dat) with(dat1,tapply(dat,list(pbnr),FUN=diff)) #10023 10028 10053 # 93 1809 191 library(plyr) ddply(dat1,.(pbnr),mutate,Datediff=diff(dat)) # pbnr dat dep dys sop ago mis age female Datediff #1 10023 1994-02-21 0.75 1.00 0.50 0.50 0.75 35 1 93 #2 10023 1994-05-25 0.75 1.00 0.50 0.50 0.75 35 1 93 #3 10028 1994-02-01 2.00 1.75 3.00 0.50 1.50 42 1 1809 #4 10028 1999-01-15 1.25 0.75 2.25 0.50 0.25 42 1 1809 #5 10053 1994-03-16 2.50 0.75 1.25 0.50 1.25 22 1 191 #6 10053 1994-09-23 3.25 1.25 1.25 0.75 2.25 22 1 191
#or dat2<-aggregate(dat~pbnr,data=dat1,diff) colnames(dat2)[2]<- "Datediff" join(dat1,dat2,by="pbnr") # pbnr dat dep dys sop ago mis age female Datediff #1 10023 1994-02-21 0.75 1.00 0.50 0.50 0.75 35 1 93 #2 10023 1994-05-25 0.75 1.00 0.50 0.50 0.75 35 1 93 #3 10028 1994-02-01 2.00 1.75 3.00 0.50 1.50 42 1 1809 #4 10028 1999-01-15 1.25 0.75 2.25 0.50 0.25 42 1 1809 #5 10053 1994-03-16 2.50 0.75 1.25 0.50 1.25 22 1 191 #6 10053 1994-09-23 3.25 1.25 1.25 0.75 2.25 22 1 191 A.K. Hi, I am new to this forum, and have a problem. I have data that looks like this: pbnr dat dep dys sop ago mis age female 1 10023 1994-02-21 0.75 1.00 0.50 0.50 0.75 35 1 2 10023 1994-05-25 0.75 1.00 0.50 0.50 0.75 35 1 3 10028 1994-02-01 2.00 1.75 3.00 0.50 1.50 42 1 4 10028 1999-01-15 1.25 0.75 2.25 0.50 0.25 42 1 5 10053 1994-03-16 2.50 0.75 1.25 0.50 1.25 22 1 6 10053 1994-09-23 3.25 1.25 1.25 0.75 2.25 22 1 ..... And I want to know how many days each person (pbnr) has been in therapy. row 1 is first a date for person 10023 and row 2 the second but what do I do now???? Thanks for you help!! Sophie ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
