Using lubridate, how to calculate the last day of the previous quarter for a given date?
The below formula doesn't seem to work for Nov 3rd, 2014 (other dates work)
library(lubridate)
date = as.POSIXct("2014-11-03")
date - days(day(date)) - months(month(date) %% 3 - 1)
# NA
Interesting enough, changing order works:
date - months(month(date) %% 3 - 1) - days(day(date))
# "2014-09-30 UTC"
Here are some possibilities with functions from packages zoo and timeDate, and base R. The zoo code was improved by @G.Grothendieck, and he also suggested the base alternative (thanks a lot!). I leave the lubridate solution(s) to someone else.
First, use class yearqtr in package zoo to represent the quarterly data. You may then use as.Date.yearqtr and the frac argument "which is a number between 0 and 1 inclusive that indicates the fraction of the way through the period that the result represents. The default is 0 which means the beginning of the period" (see ?yearqtr, and ?yearmon for frac).
Step by step:
library(zoo)
date <- as.Date("2014-11-03")
# current quarter
current_q <- as.yearqtr(date)
current_q
# [1] "2014 Q4"
# first date in current quarter
first_date_current_q <- as.Date(current_q, frac = 0)
first_date_current_q
# [1] "2014-10-01"
# last date in previous quarter
last_date_prev_q <- first_date_current_q - 1
last_date_prev_q
# [1] "2014-09-30"
And a short version by @G.Grothendieck (thanks!)
as.Date(as.yearqtr(date)) - 1
# [1] "2014-09-30"
A nice base R solution by @G.Grothendieck
as.Date(cut(date, "quarter")) - 1
# [1] "2014-09-30"
Another possibility is to use timeFirstDayInQuarter and timeLastDayInQuarter functions in package timeDate:
library(timeDate)
timeLastDayInQuarter(timeFirstDayInQuarter(date) - 1)
# GMT
# [1] [2014-09-30]