How to get equally spaced intervals when counting factors? - r

Question

I have some difficulties to create an time interval with 30 min breaks beginning either with the full hour 00 or full hour 00 and 30 min:
For instance:
library(reshape2)
library(dplyr)
# Given some data which resemble the original data
foo <- data.frame(start.time = c("2012-02-01 13:47:00",
"2012-02-01 14:02:00",
"2012-02-01 14:20:00",
"2012-02-01 14:40:00",
"2012-02-01 15:08:00",
"2012-02-01 16:01:00",
"2012-02-01 16:02:00",
"2012-02-01 16:20:00",
"2012-02-01 17:09:00",
"2012-02-01 18:08:00",
"2012-02-01 18:20:00",
"2012-02-01 19:08:00"
),
employee = c("mike","john","john","steven","mike","mike","mike","steven","mike","steven","mike","mike"))
start.time employee
#1 2012-02-01 13:47:00 mike
#2 2012-02-01 14:02:00 john
#3 2012-02-01 14:20:00 john
#4 2012-02-01 14:40:00 steven
#5 2012-02-01 15:08:00 mike
#6 2012-02-01 16:01:00 mike
#7 2012-02-01 16:02:00 mike
#8 2012-02-01 16:20:00 steven
#9 2012-02-01 17:09:00 mike
#10 2012-02-01 18:08:00 steven
#11 2012-02-01 18:20:00 mike
#12 2012-02-01 19:08:00 mike
# change factor to POSIXct
foo$start.time <- as.POSIXct(foo$start.time)
# long to wide
my_emp<- dcast(foo, start.time ~ employee, fun.aggregate = length)
# 30 min breaks
my_emp_ag<- my_emp %>% group_by(start.time = as.POSIXct(cut(start.time, breaks="30 min"))) %>%
summarize(john = sum(john ),mike = sum(mike ),steven = sum(steven))
# Missing intervalls
miss_interval <- data.frame(start.time=seq(from = min(as.POSIXct(my_emp$start.time)), to= max(as.POSIXct(my_emp$start.time)), by = "30 mins"))
# join old woth new
substitited <- left_join(miss_interval,my_emp_ag,by=c('start.time'))
# change NA to zero
substitited[is.na(substitited)] <- 0
start.time john mike steven
1 2012-02-01 13:47:00 1 1 0
2 2012-02-01 14:17:00 1 0 1
3 2012-02-01 14:47:00 0 1 0
4 2012-02-01 15:17:00 0 0 0
5 2012-02-01 15:47:00 0 2 0
6 2012-02-01 16:17:00 0 0 1
7 2012-02-01 16:47:00 0 1 0
8 2012-02-01 17:17:00 0 0 0
9 2012-02-01 17:47:00 0 0 1
10 2012-02-01 18:17:00 0 1 0
11 2012-02-01 18:47:00 0 1 0
which is almost as desired 2012-02-01 13:30:00 2012-02-01 14:00:00 and so on.

Answer 1

library(data.table)
library(lubridate)
setDT(foo)[, `:=` (
round.time = {
todate = ymd_hms(start.time)
rounddate = floor_date(todate, "30 minutes")
}
)]
start.time employee round.time
1: 2012-02-01 13:47:00 mike 2012-02-01 13:30:00
2: 2012-02-01 14:02:00 john 2012-02-01 14:00:00
3: 2012-02-01 14:20:00 john 2012-02-01 14:00:00
4: 2012-02-01 14:40:00 steven 2012-02-01 14:30:00
5: 2012-02-01 15:08:00 mike 2012-02-01 15:00:00
6: 2012-02-01 16:01:00 mike 2012-02-01 16:00:00
7: 2012-02-01 16:02:00 mike 2012-02-01 16:00:00
8: 2012-02-01 16:20:00 steven 2012-02-01 16:00:00
9: 2012-02-01 17:09:00 mike 2012-02-01 17:00:00
10: 2012-02-01 18:08:00 steven 2012-02-01 18:00:00
11: 2012-02-01 18:20:00 mike 2012-02-01 18:00:00
12: 2012-02-01 19:08:00 mike 2012-02-01 19:00:00