R/Qmintrend.R

In maibrittbergh/dischanalyst: Analyses Hydrological Data, especially Discharge Data

#' Trend of Annual Discharge Minimum Values since begin of Measurements
#'
#'@param data list; contains all stations that the discharge analysis should consider. List can be created by \link[dischanalyst]{grdc_list}. Each entry of the list contains the existing discharge measurements (as numeric) and the corresponding dates (as character) for the station.
#'@param station character; Name of the Station e.g. "COCHEM" - must be named equally like list entry in data.
#'@param mod numeric; possible input: 1,2,3. default value: 1; output of both: \link[zyp]{zyp.trend.vector}, \link[stats]{lm}. Defines the way to calculate intercept and slope. For mod=2  \link[zyp]{zyp.trend.vector} with PreWhitening by "yuepilon-method" is used. Sen-Slope-Approach used to define direction of the trend and the significance is  determined by Kendall's P-Value computed for the final detrendet time series. For mod=3: \link[stats]{lm} with a least squares approach is used.

#' @import ggplot2
#' @import zyp
#' @import stats
#'
#' @examples
#' \dontrun{ Qmintrend(mosel, "COCHEM")}
#'
Qmintrend=function(data, station, mod=1) {

  nbr=which(names(data)==station)
  val=data[[nbr]]
  abs_min=min(data[[nbr]][,2])

  year_one=as.numeric(substring(as.character(data[[nbr]][1,1]),1,4))
  length=length(data[[nbr]][,1])
  last_year=as.numeric(substring(as.character(data[[nbr]][length,1]),1,4))
  years=c(year_one:last_year)
  l=length(years)
  q_min=rep(0, l)
  for ( i in 1:l){
    year=as.character(years[i])
    j=grep(year, data[[nbr]][,1])
    Val=data[[nbr]][,2][j]
    q_min[i]=min(Val)
  }
  results=data.frame(years, q_min)
  model= min_trend(data, station)


  if(mod==1){
    titl=paste("Yuepilon and Linear Trend of Minimum Values at",station)
    cap=paste("Absolute Minimum is: ", abs_min, "slope: Trend Line- Sens Sloap:",model$slope_zyp,"slope: Trend Line- Least Squares:", model$slope_lm)
    plot=ggplot(results)+geom_line(mapping=aes(x=years,y=q_min, group=1, col="a"), show.legend  =TRUE)+labs(title=titl, subtitle=paste("from", year_one, "to", last_year), x="Years" , y="Minimum Discharge Value", caption=cap)+
      geom_abline(aes(intercept = model$intercept_zyp, slope= model$slope_zyp,  col="b"), show.legend=TRUE)+
      geom_abline(aes(intercept= model$intercept_lm, slope=model$slope_lm,col="c"), show.legend=TRUE)+  scale_color_manual(name = "Legend:   ",
                                                                                                                           labels=c("Minimum values", "Trend Line - Sens Sloap",
                                                                                                                                    "Trend Line-Least Squares"), values=c("a"="#F8766D","b"= "#00BDD0", "c"="darkblue"), guide="legend")+ theme(legend.position = "bottom" )

  }else if (mod==2){

    titl=paste("Yuepilon  Trend of Minimum Values at",station)
    cap=paste("Absolute Minimum is: ", abs_min, "slope: Trend Line- Sens Sloap:",model$slope_zyp)
    plot=ggplot(results)+geom_line(mapping=aes(x=years,y=q_min, group=1, col="a"), show.legend  =TRUE)+labs(title=titl, subtitle=paste("from", year_one, "to", last_year), x="Years" , y="Minimum Discharge Value", caption=cap)+
      geom_abline(aes(intercept = model$intercept_zyp, slope= model$slope_zyp,  col="b"), show.legend=TRUE)+
      scale_color_manual(name = "Legend:   ",
                         labels=c("Minimum values", "Trend Line - Sens Sloap"
                         ), values=c("a"="#F8766D","b"= "#00BDD0"), guide="legend")+ theme(legend.position = "bottom" )
  }else if(mod==3){

    titl=paste("Linear Trend of Minimum Values at",station)
    cap=paste("Absolute Minimum is: ", abs_min,"slope: Trend Line- Least Squares:", model$slope_lm)
    plot=ggplot(results)+geom_line(mapping=aes(x=years,y=q_min, group=1, col="a"), show.legend  =TRUE)+labs(title=titl, subtitle=paste("from", year_one, "to", last_year), x="Years" , y="Minimum Discharge Value", caption=cap)+
      geom_abline(aes(intercept= model$intercept_lm, slope=model$slope_lm,col="c"), show.legend=TRUE)+  scale_color_manual(name = "Legend:   ",
                                                                                                                           labels=c("Minimum values",
                                                                                                                                    "Trend Line-Least Squares"), values=c("a"="#F8766D", "c"="darkblue"), guide="legend")+ theme(legend.position = "bottom" )
  }




  return(plot)


}