Transforming longitudinal data for time-to-event analysis in R - r

Question

I am trying to reformat longitudinal data for a time to event analysis. In the example data below, I simply want to find the earliest week that the result was “0” for each ID.
The specific issue I am having is how to patients that don't convert to 0, and had either all 1's or 2's. In the example data, patient J has all 1's.
#Sample data
have<-data.frame(patient=rep(LETTERS[1:10], each=9),
week=rep(0:8,times=10),
result=c(1,0,2,rep(0,6),1,1,2,1,rep(0,5),1,1,rep(0,7),1,rep(0,8),
1,1,1,1,2,1,0,0,0,1,1,1,rep(0,6),1,2,1,rep(0,6),1,2,rep(0,7),
1,rep(0,8),rep(1,9)))
patient week result
A 0 1
A 1 0
A 2 2
A 3 0
A 4 0
A 5 0
A 6 0
A 7 0
A 8 0
B 0 1
B 1 0
... .....
J 6 1
J 7 1
J 8 1
I am able to do this relatively straightforward process with the following code:
want<-aggregate(have$week, by=list(have$patient,have$result), min)
want<-want[which(want[2]==0),]
but realize if someone does not convert to 0, it excludes them (in this example, patient J is excluded). Instead, J should be present with a 1 in the second column and an 8 in the third column. Instead it of course is omitted
print(want)
Group.1 Group.2 x
A 0 1
B 0 4
C 0 2
D 0 1
E 0 6
F 0 3
G 0 3
H 0 2
I 0 1
#But also need
J 1 8
Pursuant to guidelines on posting here, I did work to solve this, am able to get what I need very inelegantly:
mins<-aggregate(have$week, by=list(have$patient,have$result), min)
maxs<-aggregate(have$week, by=list(have$patient,have$result), max)
want<-rbind(mins[which(mins[2]==0),],maxs[which(maxs[2]==1&maxs[3]==8),])
This returns the correct desired dataset, but the coding is terrible and not sustainable as I work with other datasets (i.e. datasets with different timeframes since I have to manually put in maxsp[3]==8, etc).
Is there a more elegant or systematic way to approach this data manipulation issue?

Answer 1

We can write a function to select a row from the group.
select_row <- function(result, week) {
if(any(result == 0)) which.max(result == 0) else which.max(week)
}
This function returns the index of first 0 value if it is present or else returns index of maximum value of week.
and apply it to all groups.
library(dplyr)
have %>% group_by(patient) %>% slice(select_row(result, week))
# patient week result
# <fct> <int> <dbl>
# 1 A 1 0
# 2 B 4 0
# 3 C 2 0
# 4 D 1 0
# 5 E 6 0
# 6 F 3 0
# 7 G 3 0
# 8 H 2 0
# 9 I 1 0
#10 J 8 1