Useful helper functions?

[omuelle]

I have a few helper functions in the kofbts and kofbarometer package I use on a regular basis. I'm trying to find a place for them. Would they fit in tstools?

#' Returns Date object given year and month. The day is set to 1.
ymDate <- function(year, month)
{
  as.Date(paste0(year, "-", month, "-1"))
}

dateToTime <- function(date)
{
  data.table::year(date) + (data.table::month(date) - 1)/12
}

timeToDate <- function(time)
{
  time <- round(time, 3)
  ymDate(floor(time), round((time - floor(time)) / (1/12)) + 1)
}

startTime <- function(ts)
{
  time(ts)[1]
}

endTime <- function(ts)
{
  time(ts)[length(ts)]
}

startDate <- function(ts)
{
  timeToDate(startTime(ts))
}

endDate <- function(ts)
{
  timeToDate(endTime(ts))
}

frequencyDate <- function(date, frequency)
{
  ymDate(year(date), (ceiling(month(date) / (12/frequency)) - 1) * (12/frequency) + 1)
}

toMonthlySeries <- function(x, fill_last_quarter = F)
{
  vals <- unlist(lapply(as.vector(x), function(val) c(val, NA, NA)))
  if(!fill_last_quarter) {
    vals <- vals[1:(length(vals)-2)]
  }
  ts(vals, start = startTime(x), frequency = 12)
}

#' Add a number of months to a given date. Return NA if the resulting Date does not exist,
#' for example if the day is the 31th and the new month doesn't have 31 days. "months" can
#' be negative.
#' 
#' @param date   Date or character representing a Date.
#' @param months integer, number of months to add, can be negative.
#' @return       Date with months added to date
#' @export
addMonths <- function(date, months) 
{
  m <- data.table::month(date)-1+months
  add_this <- m%%12+1

  d_str <- paste0(data.table::year(date)+m%/%12, "-",
                  ifelse(nchar(add_this) == 1, paste0("0", add_this), add_this), "-",
                  data.table::mday(date))

  tryCatch({as.Date(d_str)}, error = function(e) NA)
}