Detect consequitive minutes in POSIXct in R-CodePudding

Suppose I have

dt <- as.POSIXct(c("2020-01-01 09:30:00", 
                   "2020-01-01 09:31:00", 
                   "2020-01-01 09:35:00", 
                   "2020-01-01 09:36:00", 
                   "2020-01-01 09:37:00", 
                   "2020-01-01 09:40:00", 
                   "2020-01-01 09:50:00", 
                   "2020-01-01 09:51:00", 
                   "2020-01-01 09:52:00"))

and I want to find the first minute for every time say 3 consecutive minutes are in dt, i.e.

"2020-01-01 09:35:00" "2020-01-01 09:50:00".

How would I be able to do this?

CodePudding user response：

Here is a base R approach -

with(rle(as.integer(c(difftime(dt[-1],dt[-length(dt)],units = 'mins'),0)) == 1), 
    dt[!duplicated(rep(seq_along(values), lengths)) & 
        rep(lengths >= 2 & values, lengths)])

#[1] "2020-01-01 09:35:00  08" "2020-01-01 09:50:00  08"

difftime calculates difference between consecutive timestamps.
Using rle we calculate lengths whose difference between timestamp is 1 minute.
Return only the starting timestamp of groups where length is greater than 2.