R/RProjects/HITHATStats/R/mh1.12.R

In jlthomps/EflowStats: Returns HIT/HAT Hydrologic Indicator stats for a given set of data

#' Function to return the MH1-MH12 hydrologic indicator statistics for a given data frame
#' 
#' This function accepts a data frame that contains columns named "discharge", "year_val" and "month_val" and 
#' calculates the mean (or median - use preference option) maximum flows for each month across all years. 
#' Compute the maximums for each month. For example, MH1 is the mean of the maximums of all January flow values.
#' 
#' @param qfiletemp data frame containing a "discharge" column containing daily flow values
#' @return mh1.12 data frame containing the mean or medians for each month
#' @export
#' @examples
#' load_data<-paste(system.file(package="HITHATStats"),"/data/obs_data.csv",sep="")
#' qfiletemp<-read.csv(load_data)
#' mh1.12(qfiletemp)
mh1.12 <- function(qfiletemp) {
  maxbymonyr <- aggregate(qfiletemp$discharge, list(qfiletemp$year_val, qfiletemp$month_val), FUN = max, na.rm=TRUE)
  colnames(maxbymonyr) <- c("Year","Month","maxmo")
  meanmaxbymon <- aggregate(maxbymonyr$maxmo, list(maxbymonyr$Month), FUN = mean, na.rm=TRUE)
  colnames(meanmaxbymon) <- c("Month","meanmax")
  mh1 <- meanmaxbymon[1,2]
  mh2 <- meanmaxbymon[2,2]
  mh3 <- meanmaxbymon[3,2]
  mh4 <- meanmaxbymon[4,2]
  mh5 <- meanmaxbymon[5,2]
  mh6 <- meanmaxbymon[6,2]
  mh7 <- meanmaxbymon[7,2]
  mh8 <- meanmaxbymon[8,2]
  mh9 <- meanmaxbymon[9,2]
  mh10 <- meanmaxbymon[10,2]
  mh11 <- meanmaxbymon[11,2]
  mh12 <- meanmaxbymon[12,2]
  mh1.12 <- list(mh1,mh2,mh3,mh4,mh5,mh6,mh7,mh8,mh9,mh10,mh11,mh12)
  return(mh1.12)
}