CODEWITHSUNDEEP
r
Shivam Sarin
Shivam Sarin

Reputation: 551

Calculate the difference in dates in r

I have a dataframe in which there are 3 columns Alertdate, AppointmentDate and ID. The id is not unique and there multiple occurrences for alert and appointment. I want to calculate the difference in Alertdate and AppointmentDate but only for the first occurrence of ID. Example

ID  Alertdate  AppointmentDate  NBD

*1   01/01/2000    04/01/2000        3*

1   02/01/2000    04/01/2000        2

*2   01/01/2000    04/01/2000        3*

2   01/01/2000    05/01/2000        4

For the above sample data I just need row1 and row3 in my resulting output.

Upvotes: 1

Views: 55

Answers (1)

user2974951
user2974951

Reputation: 10375

In case you need to calculate NBD first

dat=read.table(text="
ID Alertdate AppointmentDate NBD
1 01/01/2000 04/01/2000 3
1 02/01/2000 04/01/2000 2
2 01/01/2000 04/01/2000 3
2 01/01/2000 05/01/2000 4",h=T)

dat$Alertdate=as.Date(dat$Alertdate,format="%d/%m/%Y")
dat$AppointmentDate=as.Date(dat$AppointmentDate,format="%d/%m/%Y")
dat$NBD=as.numeric(dat$AppointmentDate-dat$Alertdate)

In case the table is not sorted

dat=dat[order(dat$ID,dat$Alertdate),]

finally

do.call(rbind,by(dat,list(dat$ID),function(x){x[1,]}))
  ID  Alertdate AppointmentDate NBD
1  1 01/01/2000      04/01/2000   3
2  2 01/01/2000      04/01/2000   3

Upvotes: 3

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