Find the quarter or year + quarter of a date in R. The function is a modified version of quarter from lubridate.

quarter_year.R

quarter_year <- function(x, with_year = FALSE) {
  require(lubridate)
  m <- month(x)
  quarters <- c("1" = 1, 
                "2" = 1, 
                "3" = 1, 
                "4" = 2, 
                "5" = 2, 
                "6" = 2, 
                "7" = 3, 
                "8" = 3, 
                "9" = 3, 
                "10" = 4, 
                "11" = 4, 
                "12" = 4)
  if (isTRUE(with_year)){
    q <- unname(quarters[m])
    y <- year(x)
    as.numeric(paste0(y, ".", q))
  } else unname(quarters[m])
}