Trying to shift entries in a column

Question

I am trying to move entries in my column around to set them up as start/stop times. The first row for each id is set up fine but I need to shift the rest down and over for this to work as I am trying.

I have tried using dplyr and mutating the entries into new columns but the problem is the time entry is in another column so I am trying to work around that.

#This is what my data looks like
mydata<-data.frame(id=c(rep(1,3),rep(2,2)),baseline=c(rep("2018-07-14",3),
                                                      rep("2018-06-16",2)),
                   date=c("2018-08-23","2018-09-20","2018-10-05","2018-07-04","2018-08-08"))
head(mydata)

expecteddata<-data.frame(id=c(rep(1,3),rep(2,2)),
                   start=c("2018-07-14","2018-08-23","2018-09-20","2018-06-16","2018-07-04"),
                   end=c("2018-08-23","2018-09-20","2018-10-05","2018-07-04","2018-08-08"))
head(expecteddata)

This is what I am hoping to get. It also might be nice to increment start times since different rows would belong to different risk sets but that is a different issue. Any help or pointers would be greatly appreciated on how I can proceed.

score 0 · Accepted Answer · answered Jul 24 '19 at 23:36

Ensure that the date variables are the correct class and try:

library(dplyr)

mydata %>%
  group_by(id) %>% 
  mutate(baseline =  lag(date, default = first(baseline))) %>%
  rename(start = baseline, end = date)

# A tibble: 5 x 3
# Groups:   id [2]
     id start      end       
  <dbl> <date>     <date>    
1     1 2018-07-14 2018-08-23
2     1 2018-08-23 2018-09-20
3     1 2018-09-20 2018-10-05
4     2 2018-06-16 2018-07-04
5     2 2018-07-04 2018-08-08

Trying to shift entries in a column

1 Answers1