Hi,
Try:
evt_c.1<- read.table(text="
patient_id responsed_at
1 2010-5
1 2010-7
1 2010-8
1 2010-9
2 2010-5
2 2010-6
2 2010-7
",sep="",header=TRUE,stringsAsFactors=FALSE)
lst1<-split(evt_c.1,evt_c.1$patient_id)
res<-do.call(rbind,lapply(lst1,function(x)
{x1<-as.numeric(gsub(".*\\-","",x[,2])); x$t<-c(0,cumsum(diff(x1)));x}))
row.names(res)<-1:nrow(res)
res
# patient_id responsed_at t
#1 1 2010-5 0
#2 1 2010-7 2
#3 1 2010-8 3
#4 1 2010-9 4
#5 2 2010-5 0
#6 2 2010-6 1
#7 2 2010-7 2
#or
library(plyr)
res2<-mutate(evt_c.1,t=ave(as.numeric(gsub(".*\\-","",responsed_at)),patient_id,FUN=function(x)
c(0,cumsum(diff(x)))))
res2
# patient_id responsed_at t
#1 1 2010-5 0
#2 1 2010-7 2
#3 1 2010-8 3
#4 1 2010-9 4
#5 2 2010-5 0
#6 2 2010-6 1
#7 2 2010-7 2
identical(res,res2)
#[1] TRUE
A.K.
________________________________
From: GUANGUAN LUO <guanguan...@gmail.com>
To: arun <smartpink...@yahoo.com>
Sent: Wednesday, April 17, 2013 8:32 AM
Subject: Re: how to change the date into an interval of date?
thank you, and now i've got a table like this
> dput(head(evt_c.1,5)) structure(list(responsed_at = c("2010-05", "2010-07",
> "2010-08",
"2010-10", "2010-11"), patient_id = c(2L, 2L, 2L, 2L, 2L), number = c(1,
2, 3, 4, 5), response_id = c(77L, 1258L, 2743L, 4499L, 6224L), session_id =
c(2L, 61L, 307L, 562L, 809L), login = c(3002, 3002, 3002, 3002, 3002),
clinique_basdai.fatigue = c(4, 5, 5, 6, 4),
which i want is to add a column "t", for example
now my table is like this:
patient_id responsed_at
1 2010-5
1 2010-7
1 2010-8
1 2010-9
2 2010-5
2 2010-6
2 2010-7
after add the column "t"
paient_id responsed_at t
1 2010-5 0
1 2010-7 2
1 2010-8 3
1 2010-9 4
2 2010-5 0
2 2010-6 1
2 2010-7 2
Le 17 avril 2013 14:23, arun <smartpink...@yahoo.com> a écrit :
Hi,
>format() is one way.
>library(zoo)
> as.yearmon(dat1$responsed_at)
>#[1] "May 2010" "Jul 2010" "Aug 2010" "Oct 2010" "Nov 2010" "Dec 2010"
> #[7] "Jan 2011" "Feb 2011" "Mar 2011" "Apr 2011" "Jun 2011" "Jul 2011"
>#[13] "Aug 2011" "Sep 2011" "Oct 2011" "Nov 2011" "Dec 2011" "Jan 2012"
>#[19] "Mar 2012" "May 2010"
>A.K.
>
>
>
>
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