R/low_yearly_mean.R

In HARPgroup/cbp6:

#' Lowest Yearly Mean Metric Function 
#' @description Calculates the lowest yearly mean flow of dataframe - must be trimmed to water year 
#' @param data a dataframe with hydrologic data 
#' @return The lowest yearly mean flow
#' @import lubridate
#' @import lfstat
#' @import stats
#' @import zoo
#' @export low_yearly_mean

low_yearly_mean <- function(data) {
  #setup
  data$year <- year(ymd(data$date))
  data$month <- month(ymd(data$date))
  data$day <- day(ymd(data$date))
  
  flows_model1 <- zoo(data$flow, order.by = data$date)
  DoR <- fn_iha_DOR_Year(flows_model1);
  
  model1.data <- data.frame(data$day, data$month, data$year, data$flow)
  names(model1.data) <- c('day', 'month', 'year', 'flow')
  model1river <- createlfobj(model1.data, hyearstart = 10, baseflow = TRUE, meta = NULL)
  lf_model <- aggregate(model1river$flow, by = list(model1river$hyear), FUN = mean)
  colnames(lf_model) <- c('Water_Year', 'Mean_Flow')
  #calculation
  lf_model <- which(lf_model["Water_Year"] == DoR)
  lf_model <- lf_model[lf_model_flow,2]
  return(lfmin)
}