Time Series within R (ColumnSorting) - r

Question

I have a csv of real-time data inputs with timestamps and I am looking to group these data in a time series of 30 mins for analysis.
A sample of the real-time data is
Date:
2019-06-01 08:03:04
2019-06-01 08:20:04
2019-06-01 08:33:04
2019-06-01 08:54:04
...
I am looking to group them in a table with a step increment of 30 mins (i.e. 08:30, 09:00, etc..) to seek out the number of occurences during each period. I created a new csv file to access through R. This is so that I will not corrupt the formatting of the orginal dataset.
Date:
2019-06-01 08:00
2019-06-01 08:30
2019-06-01 09:00
2019-06-01 09:30
I have firstly constructed a list of 30 mins intervals by:
sheet_csv$Date <- as.POSIXct(paste(sheet_csv$Date), format = "%Y-%m-%d %H:%M", tz = "GMT") #to change to POSIXct
sheet_csv$Date <- timeDate::timeSequence(from = "2019-06-01 08:00", to = "2019-12-03 09:30", by = 1800,
format = "%Y-%m-%d %H:%M", zone = "GMT")
I encountered an error "Error in x[[idx]][[1]] : this S4 class is not subsettable" for this interval.
I am relatively new to R. Please do help out where you can. Greatly Appreciated.

Answer 1

You probably don't need the timeDate package for something like this. One package that is very helpful to manipulate dates and times is lubridate - you may want to consider going forward.
I used your example and added another date/time for illustration.
To create your 30 minute intervals, you could use cut and seq.POSIXt to create a sequence of date/times with 30 minute breaks. I used your minimum date/time to start with (rounding down to nearest hour) but you can also specify another date/time here.
Use of table will give you frequencies after cut.
sheet_csv <- data.frame(
Date = c("2019-06-01 08:03:04",
"2019-06-01 08:20:04",
"2019-06-01 08:33:04",
"2019-06-01 08:54:04",
"2019-06-01 10:21:04")
)
sheet_csv$Date <- as.POSIXct(sheet_csv$Date, format = "%Y-%m-%d %H:%M:%S", tz = "GMT")
as.data.frame(table(cut(sheet_csv$Date,
breaks = seq.POSIXt(from = round(min(sheet_csv$Date), "hours"),
to = max(sheet_csv$Date) + .5 * 60 * 60,
by = "30 min"))))
Output
Var1 Freq
1 2019-06-01 08:00:00 2
2 2019-06-01 08:30:00 2
3 2019-06-01 09:00:00 0
4 2019-06-01 09:30:00 0
5 2019-06-01 10:00:00 1