#' Function to return the MA24-35 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 variability (coefficient of variation) of monthly flow values. compute the standard deviation for each month in each
#' year over the entire flow record. Divide the standard deviation by the mean for each month. Average (or median - use preference option) these values for
#' each month across all years (percent - temporal).
#'
#' @param qfiletempf data frame containing a "discharge" column containing daily flow values
#' @param pref string containing a "mean" or "median" preference
#' @return ma234.35 data frame containing the MA24-MA35 statistics for the given data frame
#' @export
#' @examples
#' qfiletempf<-sampleData
#' ma24.35(qfiletempf)
ma24.35 <- function(qfiletempf, pref = "mean") {
sdmonbyyr <- aggregate(qfiletempf$discharge, list(qfiletempf$year_val,
qfiletempf$month_val), FUN = sd, na.rm=TRUE)
colnames(sdmonbyyr) <- c("Year", "Month", "sdq")
meanmonbyyr <- aggregate(qfiletempf$discharge, list(qfiletempf$year_val,
qfiletempf$month_val), FUN = mean, na.rm=TRUE)
colnames(meanmonbyyr) <- c("Year", "Month", "meanq")
dfcvmonbyyr <- data.frame(meanmonbyyr$Year, meanmonbyyr$Month,
sdmonbyyr$sdq, meanmonbyyr$meanq)
colnames(dfcvmonbyyr) <- c("Year", "Month", "sdq",
"meanq")
cvmonbyyr <- dfcvmonbyyr$sdq/dfcvmonbyyr$meanq
dfcvmonbyyrf <- data.frame(dfcvmonbyyr, cvmonbyyr)
colnames(dfcvmonbyyrf) <- c("Year", "Month", "sdq",
"meanq", "cvq")
if (pref == "median") {
medmoncv <- aggregate(dfcvmonbyyrf$cvq, list(dfcvmonbyyrf$Month),
median, na.rm=TRUE)
ma24.35 <- data.frame(medmoncv[2] * 100)
}
else {
meanmoncv <- aggregate(dfcvmonbyyrf$cvq, list(dfcvmonbyyrf$Month),
mean, na.rm=TRUE)
ma24.35 <- data.frame(meanmoncv[2] * 100)
}
return(ma24.35)
}
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