[R] Calculate days with R

[arun]

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