Data Structure for Sequence of Event Analysis in R - arrays

Question

The code below creates a sample dataframe to illustrate my problem. I have a time stamped list of events.
set.seed(100)
mydf<-data.frame(time=(1:1000),event = sample(1:10,10000,replace=TRUE))
mydf
time event
1 6
2 5
3 7
4 8
5 4
6 2
7 10
8 9
9 4
10 6
11 4
12 3
13 8
14 3
15 9
16 1
17 7
18 3
19 8
20 10
I am trying to create a new variable that lists the previous events in a specified window. say the window is size 10. I would like to create the dataframe below. My ultimate goal is to prepare my data for sequence of events analysis.
time event eventList
1 6 NA
2 5 NA
3 7 NA
4 8 NA
5 4 NA
6 2 NA
7 10 NA
8 9 NA
9 4 NA
10 6 NA
11 4 {6,5,7,8,4,2,10,9,4,6}
12 3 {5,7,8,4,2,10,9,4,6,4}
13 8 {7,8,4,2,10,9,4,6,4,3}
14 3 {8,4,2,10,9,4,6,4,3,8}
15 9 {4,2,10,9,4,6,4,3,8,3}
16 1 {2,10,9,4,6,4,3,8,3,9}
17 7 {10,9,4,6,4,3,8,3,9,1}
18 3 {9,4,6,4,3,8,3,9,1,7}
19 8 {4,6,4,3,8,3,9,1,7,8}
20 10 {6,4,3,8,3,9,1,7,8,10}

Answer 1

The last three rows do not match , could you please check your expected output
mydf=read.table(text="
time event
1 6
2 5
3 7
4 8
5 4
6 2
7 10
8 9
9 4
10 6
11 4
12 3
13 8
14 3
15 9
16 1
17 7
18 3
19 8
20 10",header=TRUE,stringsAsFactors=FALSE)
windowSize = 10
mydf$eventList = do.call(rbind,lapply(mydf$time,function(x) {
ifelse(x<windowSize,NA,paste0("{", paste0(mydf[ tail(1:x,windowSize) ,"event"],collapse=",") , "}"))
}))
mydf
# time event eventList
#1 1 6 <NA>
#2 2 5 <NA>
#3 3 7 <NA>
#4 4 8 <NA>
#5 5 4 <NA>
#6 6 2 <NA>
#7 7 10 <NA>
#8 8 9 <NA>
#9 9 4 <NA>
#10 10 6 {6,5,7,8,4,2,10,9,4,6}
#11 11 4 {5,7,8,4,2,10,9,4,6,4}
#12 12 3 {7,8,4,2,10,9,4,6,4,3}
#13 13 8 {8,4,2,10,9,4,6,4,3,8}
#14 14 3 {4,2,10,9,4,6,4,3,8,3}
#15 15 9 {2,10,9,4,6,4,3,8,3,9}
#16 16 1 {10,9,4,6,4,3,8,3,9,1}
#17 17 7 {9,4,6,4,3,8,3,9,1,7}
#18 18 3 {4,6,4,3,8,3,9,1,7,3}
#19 19 8 {6,4,3,8,3,9,1,7,3,8}
#20 20 10 {4,3,8,3,9,1,7,3,8,10}

Answer 2

I am assuming someone will come up with a more R way of going this, reducing your runtime. Meanwhile you can try this:
for (i in 1:nrow(mydf)){
if(i<=w){
mydf$eventList[i] = NA
}
else {
mydf$eventList[i] = list(mydf$event[c((i-w):i)])
}
}