First day of the month from a POSIXct date time using lubridate

Question

Given a POSIXct date time, how do you extract the first day of the month for aggregation?

library(lubridate)

full.date <- ymd_hms(\"2013-01-01 00:00:21\"         


        

Answer 1

I don't see a reason to use lubridate:

full.date <- as.POSIXct("2013-01-11 00:00:21", tz="GMT")

monthStart <- function(x) {
  x <- as.POSIXlt(x)
  x$mday <- 1
  as.Date(x)
}

monthStart(full.date)
#[1] "2013-01-01"