R/monitor_timeInfo.R

In PWFSLSmoke: Utilities for Working with Air Quality Monitoring Data

#' @title Get time related information for a monitor
#'
#' @description Calculate the local time for the monitor, as well as
#' sunrise, sunset and solar noon times, and create several temporal masks.
#'
#' The returned dataframe will have as many rows as the length of the incoming
#' UTC \code{time} vector and will contain the following columns:
#'
#' \itemize{
#' \item{\code{localStdTime_UTC} -- UTC representation of local \strong{standard} time}
#' \item{\code{daylightSavings} -- logical mask = TRUE if daylight savings is in effect}
#' \item{\code{localTime} -- local clock time}
#' \item{\code{sunrise} -- time of sunrise on each localTime day}
#' \item{\code{sunset} -- time of sunset on each localTime day}
#' \item{\code{solarnoon} -- time of solar noon on each localTime day}
#' \item{\code{day} -- logical mask = TRUE between sunrise and sunset}
#' \item{\code{morning} -- logical mask = TRUE between sunrise and solarnoon}
#' \item{\code{afternoon} -- logical mask = TRUE between solarnoon and sunset}
#' \item{\code{night} -- logical mask = opposite of day}
#' }
#'
#' @details
#' While the \pkg{lubridate} package makes it easy to work in local timezones,
#' there is no easy way in R to work in "Local Standard Time" (LST) as is often
#' required when working with air qualitiy data. EPA regulations mandate that
#' daily averages be calculated based on LST.
#'
#' The \code{localStdTime_UTC} is primarily for use internally and provides
#' an important tool for creating LST daily averages and LST axis labeling.
#'
#' @param ws_monitor \emph{ws_monitor} object.
#' @param monitorID Monitor ID for a specific monitor in \code{ws_monitor} --
#' optional if \code{ws_monitor} only has one monitor.
#'
#' @return A dataframe with times and masks.
#'
#' @export
#'
#' @examples
#' library(PWFSLSmoke)
#'
#' carmel <- monitor_subset(Carmel_Valley, tlim = c(20160801,20160810))
#'
#' # Create timeInfo object for this monitor
#' ti <- monitor_timeInfo(carmel)
#'
#' # Subset the data based on day/night masks
#' data_day <- carmel$data[ti$day,]
#' data_night <- carmel$data[ti$night,]
#'
#' # Build two monitor objects
#' carmel_day <- list(meta = carmel$meta, data = data_day)
#' carmel_night <- list(meta = carmel$meta, data = data_night)
#'
#' # Plot them
#' monitor_timeseriesPlot(carmel_day, shadedNight = TRUE, pch = 8, col = 'goldenrod')
#' monitor_timeseriesPlot(carmel_night, pch = 16, col = 'darkblue', add = TRUE)

monitor_timeInfo <- function(
  ws_monitor = NULL,
  monitorID = NULL
) {

  # ----- Validate parameters --------------------------------------------------

  # ws_monitor
  if ( !monitor_isMonitor(ws_monitor) ) {
    stop("Argument 'ws_monitor' is not a valid ws_monitor object.")
  } else if ( monitor_isEmpty(ws_monitor) ) {
    stop("Argument 'ws_monitor' is empty.")
  }

  if ( nrow(ws_monitor$meta) == 1 ) {
    monitorID <- ws_monitor$meta$monitorID[1]
  } else {
    if ( is.null(monitorID) ) {
      stop("Argument 'monitorID' must be defined.")
    } else if ( !monitorID %in% ws_monitor$meta$monitorID ) {
      stop(paste0("Monitor ", monitorID, " is not found in 'ws_monitor'."))
    }
    ws_monitor <- monitor_subset(ws_monitor, monitorIDs = monitorID)
  }

  # ----- Return ---------------------------------------------------------------

  timeInfo <- timeInfo(
    ws_monitor$data$datetime,
    ws_monitor$meta$longitude,
    ws_monitor$meta$latitude,
    ws_monitor$meta$timezone
  )

  return(timeInfo)

}