R/degree_time.R

In johnwoodill/nonlineartempr: Calculate daily degree days and time in each degree

#' @title Calculate time in each degree
#'
#' @description
#' \code{degree_time} returns a data frame with calculated time in each degree at one degree intervals
#' within a specified thresholds.
#' 
#' @details 
#' To generate time in each degree the data passed must be in wide format with minimum temperature 
#' column labeled as tmin and maximum temperature labeled as tmax. 
#' 
#' @param data data in wide format with minimum temperature labeled as tmin and maximum temperature labeled as tmax
#' @param thresholds threshold of temperature intervals to calculate time in each degree
#' @examples 
#' data(napa)
#' degree_time(napa, thresholds = c(0:35))
#'

degree_time <- function(data, thresholds){
  
  # Check for tmin and tmax columns
  name_check <- names(data)
  check <- ifelse(any(name_check == 'tmax') & any(name_check == 'tmin'), 1, 0)
  
  if(check != 1) {
    warning("data.frame does not contain tmax or tmin. Please provide data.frame with these columns.")
  } else {
  
    # Assign return data
    retdat <- as.data.frame(data)
    
    # ncols to add
    nc <- ncol(retdat)
    
    # Loop through each threshold
    for (i in 1:length(thresholds)){
      
      # Insert new column
      col <- paste0("tdegree", thresholds[i], "C")
      cadd <- i + nc
      b <- thresholds[i]
      retdat[, cadd] <- 0
      
      # Intervals between +- 0.5
      n   =  length(retdat$tmin)
      t0  =  rep(thresholds[i] - 0.5, n)
      t1  =  rep(thresholds[i] + 0.5, n)
      
      # Calculate time in each degree
      t0[t0 < retdat$tmin]  =  retdat$tmin[t0 < retdat$tmin]
      t1[t1 > retdat$tmax]  =  retdat$tmax[t1 > retdat$tmax]
      # Suppressing message because produces NA, which are ignored
      retdat[, cadd] <- suppressWarnings((2/pi) * (asin((t1 - retdat$tmin)/(retdat$tmax - retdat$tmin)) - 
                                  asin((t0 - retdat$tmin)/(retdat$tmax - retdat$tmin))))
      
      # If NA or less than zero, recode to zero
      retdat[, cadd] <- ifelse(is.na(retdat[, cadd]), 0, retdat[, cadd])
      retdat[, cadd] <- ifelse(retdat[, cadd] < 0 , 0, retdat[, cadd])
      
      # Round time in each degree
      retdat[, cadd] <- round(retdat[,cadd], 5)
      
      # Rename column
      colnames(retdat)[cadd] <- col
      }
  return(retdat)
  }
}