I have a large time series (in data frame form) (n=>6000) that looks like this:
time, precip
1 2005-09-30 11:45:00, 0.08
2 2005-09-30 23:45:00, 0.72
3 2005-10-01 11:45:00, 0.01
4 2005-10-01 23:45:00, 0.08
5 2005-10-02 11:45:00, 0.10
6 2005-10-02 23:45:00, 0.33
7 2005-10-03 11:45:00, 0.15
8 2005-10-03 23:45:00, 0.30
9 2005-10-04 11:45:00, 0.00
10 2005-10-04 23:45:00, 0.00
11 2005-10-05 11:45:00, 0.02
12 2005-10-05 23:45:00, 0.00
13 2005-10-06 11:45:00, 0.00
14 2005-10-06 23:45:00, 0.01
15 2005-10-07 11:45:00, 0.00
16 2005-10-07 23:45:00, 0.00
17 2005-10-08 11:45:00, 0.00
18 2005-10-08 23:45:00, 0.16
19 2005-10-09 11:45:00, 0.03
20 2005-10-09 23:45:00, 0.00
Each row has a time (YYYY-MM-DD HH:MM:SS, 12 hour timeseries) and a precipitation amount. I'd like to separate the data by storm events.
What I'd like to do is this: 1) adding a new column called "storm" 2) for each set of amount values separated by 0's, call it one storm.
For example...
Time, Precip, Storm
1 2005-09-30 11:45:00, 0.08, 1
2 2005-09-30 23:45:00, 0.72, 1
3 2005-10-01 11:45:00, 0.01, 1
4 2005-10-01 23:45:00, 0.08, 1
5 2005-10-02 11:45:00, 0.10, 1
6 2005-10-02 23:45:00, 0.33, 1
7 2005-10-03 11:45:00, 0.15, 1
8 2005-10-03 23:45:00, 0.30, 1
9 2005-10-04 11:45:00, 0.00
10 2005-10-04 23:45:00, 0.00
11 2005-10-05 11:45:00, 0.02, 2
12 2005-10-05 23:45:00, 0.00
13 2005-10-06 11:45:00, 0.00
14 2005-10-06 23:45:00, 0.01, 3
15 2005-10-07 11:45:00, 0.00
16 2005-10-07 23:45:00, 0.00
17 2005-10-08 11:45:00, 0.00
18 2005-10-08 23:45:00, 0.16, 4
19 2005-10-09 11:45:00, 0.03, 4
20 2005-10-09 23:45:00, 0.00
4) after that, my plan is to subset the data by storm event.
I am pretty new to R, so don't be afraid of pointing out the obvious. Your help would be much appreciated!
You can find the events within a storm then use rle and modify the results
# assuming your data is called rainfall
# identify whether a precipitation has been recorded at each timepoint
rainfall$storm <- rainfall$precip > 0
# do run length encoding on this storm indicator
storms < rle(rainfall$storms)
# set the FALSE values to NA
is.na(storms$values) <- !storms$values
# replace the TRUE values with a number in seqence
storms$values[which(storms$values)] <- seq_len(sum(storms$values, na.rm = TRUE))
# use inverse.rle to revert to the full length column
rainfall$stormNumber <- inverse.rle(storms)