storing lubridate intervals in a dataframe (R) - r

Question

I want to create a dataframe of 15 minute intervals over 24 hours starting with a certain inverval on several dates. I use a loop for that but instant of the actual intervals it stores the number of seconds which is not useful in my case. Is there any way to avoid this? I need the intervals to look how often timed events happen in these intervals. I found one similar question, but the answer concentrated on using lapply instead of apply, which isn't applicable here.
So here is a basic example:
begin<-as.POSIXct(rbind("2016-03-31 09:00:00","2016-04-12 09:00:00"))
end<-as.POSIXct(rbind("2016-03-31 09:15:00","2016-04-12 09:15:00"))
int<-as.interval(begin,end)
aufl<-duration(15, "mins")
Intervall=data.frame()
for (j in 1:length(int)){for (i in 1:96){Intervall[j,i]<-int_shift(int[j],aufl*(i-1))}}
Intervall

Answer 1

I created an answer, I hope this is what you are looking for. If not, please comment:
library(lubridate)
begin <- as.POSIXct(rbind("2016-03-31 09:00:00","2016-04-12 09:00:00"))
# copy begin time for loop
begin_new <- begin
# create durateion object
aufl <- duration(15, "mins")
# count times for loop
times <- 24*60/15
# create dataframe with begin time
Intervall <- data.frame(begin,stringsAsFactors = FALSE)
for (i in 1:times){
cat("test",i,"\n")
# save old time for interval calculation
begin_start <- begin_new
# add 15 Minutes to original time
begin_new <- begin_new + aufl
cat(begin_new,"\n")
# create an interval object between
new_dur <- interval(begin_start,begin_new)
# bind to original dataframe
Intervall <- cbind(Intervall,new_dur)
}
# Add column names
vec_names <- paste0("v",c(1:(times+1)))
colnames(Intervall) <- vec_names