R/datetimeToDate.R

In CentreForHydrology/CRHMr: Pre- and post- processing for CRHM

#' Converts an \R datetime to a date
#'
#' @description This is used when a \pkg{CRHMr} date is stored as a datetime (POSIXct) variable.
#' @param dataframe Required. A data frame. The first name of the column must be a POSIXct variable,
#'  which can be converted to a standard \R date.
#' @param logfile Optional. Name of the file to be used for logging the action. Normally not used.
#' @return If successful, returns a data frame where the first column is a standard \pkg{CRHMr} date.
#' If unsuccessful, returns an error.
#' @author Kevin Shook
#' @seealso \code{\link{dateToDatetime}}
#' @importFrom lubridate is.POSIXt
#' @export
#'
#' @examples
#' Badlake.radiation.daily <- aggDataframe(BadLake7376, period='daily',
#' columns=c(6,7,8), funs=c('mean'))
#' BadLake.datetime <- dateToDatetime(Badlake.radiation.daily, timezone='CST')
#' BadLake.date <- datetimeToDate(BadLake.datetime)
#'
datetimeToDate <- function(dataframe, logfile=''){
  # check parameters
  if (is.null(dataframe)) {
    stop("Missing data frame")
  }
  if (!is.POSIXt(dataframe[, 1])) {
    stop("First column is not a POSIX datetime")
  }
  dataframeName <- deparse(substitute(dataframe))

  # convert data
  datetime <- dataframe[, 1]
  data_vals <- dataframe[, -1]
  data_names <- names(dataframe[, -1])
  datevals <- paste(format(datetime, format = "%Y-%m-%d"))
  datevals <- as.Date(datevals, format = "%Y-%m-%d")
  dataframe <- data.frame(datevals, data_vals)
  names(dataframe) <- c("date", data_names)

  comment <- paste("datetimeToDate dataframe:", dataframeName, sep = "")
  result <- logAction(comment, logfile)
  if (result)
    return(dataframe)
  else
    return(result)
}