R/BiEmp.R

In MSDI: Multivariate Standardized Drought Index (MSDI)

#' Compute the empirical joint probability
#' @param X The vector of a monthly hydro-climatic variable of n years.
#' @param Y The vector of a monthly hydro-climatic variable of n years.  
#' @return The empirical joint probability time scale 
#' @export
#' @examples
#' X=runif(120, min = 0, max = 100)
#' Y=runif(120, min = 0, max = 100)
#' fit<-BiEmp(X,Y) 


BiEmp<-function (X,Y)
  
{
X=matrix(X,ncol=1)
Y=matrix(Y,ncol=1)

n=length(X)

Z=matrix(NA,nrow=length(X),ncol=1)
 
for  (k in 1:n)
{  
  Z[k]=sum((X<=X[k])&(Y<=Y[k])) 
  # Weibull
  Z[k]=Z[k]/(n+1)
  #  Gringorten   Z[k]=(Z[k]-0.44)/(n+0.12)
  
} 

return(Z)

}