HI,
Try:
dat2[,Time1:=c(0,diff(Time)),by=ID]
dat2[,CumSTime1:=cumsum(Time1),by=ID]
head(dat2,4)
# ID Time Time1 CumSTime1
#1: 1 3 0 0
#2: 1 6 3 3
#3: 1 7 1 4
#4: 1 10 3 7
A.K.
----- Original Message -----
From: bibek sharma <mbhpat...@gmail.com>
To: arun <smartpink...@yahoo.com>
Cc:
Sent: Friday, December 14, 2012 12:56 PM
Subject: Re: [R] Hello R User
Hi Arun,
Great!
Once we get, time1, I again wanna add time to its previous value for
example, wanna get 0,3 4 etc...
can I have suggestion?
On Fri, Dec 14, 2012 at 9:42 AM, arun <smartpink...@yahoo.com> wrote:
> Hi,
>
> You could also use library(data.table) to do this faster.
> dat1<-read.table(text="
> ID Time
> 1 3
> 1 6
> 1 7
> 1 10
> 1 16
> 2 12
> 2 18
> 2 19
> 2 25
> 2 28
> 2 30
> ",sep="",header=TRUE)
> library(data.table)
> dat2<-data.table(dat1)
> res<-dat2[,Time1:=c(0,diff(Time)),by=ID]
> head(res,3)
> # ID Time Time1
> #1: 1 3 0
> #2: 1 6 3
> #3: 1 7 1
>
> #Comparing different approaches:
> set.seed(55)
> dat3<-
> data.frame(ID=rep(1:1000,each=500),Value=sample(1:800,5e5,replace=TRUE))
> dat4<-data.table(dat3)
> system.time(dat3$Value1<-ave(dat3$Value,dat3$ID,FUN=function(x) c(0,diff(x))))
> # user system elapsed
> # 0.312 0.000 0.313
>
> ids<-unique(dat3$ID)
> system.time({
> for(id in ids){
> dat3$Value[dat3$ID==id]<-c(0,diff(dat3$Value[dat3$ID==id]))
> } })
> # user system elapsed
> # 36.938 0.868 37.873
>
> system.time(dat5<-dat4[,Value1:=c(0,diff(Value)),by=ID])
> # user system elapsed
> # 0.036 0.000 0.037
> head(dat5)
> # ID Value Value1
> #1: 1 439 0
> #2: 1 175 -264
> #3: 1 28 -147
> #4: 1 634 606
> #5: 1 449 -185
> #6: 1 60 -389
> head(dat3)
> # ID Value Value1
> #1 1 0 0
> #2 1 -264 -264
> #3 1 -147 -147
> #4 1 606 606
> #5 1 -185 -185
> #6 1 -389 -389
>
> A.K.
>
>
>
>
>
>
>
>
>
>
>
>
> ----- Original Message -----
> From: bibek sharma <mbhpat...@gmail.com>
> To: R help <r-help@r-project.org>
> Cc:
> Sent: Friday, December 14, 2012 10:51 AM
> Subject: [R] Hello R User
>
> Hello R User,
> In the sample data given below, time is recorded for each id
> subsequently. For the analysis, for each id, I would like to set 1st
> recorded time to zero and thereafter find the difference from previous
> time. I.e. for ID==1, I would like to see Time=0,3,1,3,6. This needs
> to be implemented to big data set.
> Any suggestions are much appreciated!
> Thanks,
> Bibek
>
> ID Time
> 1 3
> 1 6
> 1 7
> 1 10
> 1 16
> 2 12
> 2 18
> 2 19
> 2 25
> 2 28
> 2 30
>
> ______________________________________________
> 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.
>
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