R/VE.R

In hydroGOF: Goodness-of-Fit Functions for Comparison of Simulated and Observed Hydrological Time Series

# File VE.R
# Part of the hydroGOF R package, http://www.rforge.net/hydroGOF/ ; 
#                                 http://cran.r-project.org/web/packages/hydroGOF/
# Copyright 2011-2012 Mauricio Zambrano-Bigiarini
# Distributed under GPL 2 or later

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# 'VE': Volumetric Efficiency                                                  #
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# Author : Mauricio Zambrano-Bigiarini                                         #
# Started: 26-Aug-2011                                                         #
# Updates: 26-Aug-2011                                                         #
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# Reference: Criss, R. E. and Winston, W. E. (2008),                           #
#            Do Nash values have value? Discussion and alternate proposals.    #
#            Hydrological Processes, 22: 2723-2725. doi: 10.1002/hyp.7072      #
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# 'obs'   : numeric 'data.frame', 'matrix' or 'vector' with observed values
# 'sim'   : numeric 'data.frame', 'matrix' or 'vector' with simulated values
# 'Result': Mean Absolute Error between 'sim' and 'obs', in the same units of 'sim' and 'obs' 

VE <-function(sim, obs, ...) UseMethod("VE")

VE.default <- function (sim, obs, na.rm=TRUE, ...){

  if ( is.na(match(class(sim), c("integer", "numeric", "ts", "zoo", "xts"))) |
          is.na(match(class(obs), c("integer", "numeric", "ts", "zoo", "xts")))
     ) stop("Invalid argument type: 'sim' & 'obs' have to be of class: c('integer', 'numeric', 'ts', 'zoo', 'xts')")    
      
  if ( length(obs) != length(sim) ) 
	 stop("Invalid argument: 'sim' & 'obs' doesn't have the same length !")
	 
  vi <- valindex(sim, obs)
     
  obs <- obs[vi]
  sim <- sim[vi]  
  
  denominator <- sum(obs, na.rm=na.rm)
  
  if (denominator != 0) {      
     ve <- 1 - ( sum( abs(sim-obs) ) / denominator )     
   } else {
       ve <- NA
       warning("'sum((obs)=0' => it is not possible to compute 'VE'")  
     } # ELSE end
     
   return(ve)      
     
} # 'VE.default' end
  
  
VE.matrix <- function (sim, obs, na.rm=TRUE, ...){

  # Checking that 'sim' and 'obs' have the same dimensions
  if ( all.equal(dim(sim), dim(obs)) != TRUE )
    stop( paste("Invalid argument: dim(sim) != dim(obs) ( [", 
          paste(dim(sim), collapse=" "), "] != [", 
          paste(dim(obs), collapse=" "), "] )", sep="") )

  ve <- rep(NA, ncol(obs))       
          
  ve <- sapply(1:ncol(obs), function(i,x,y) { 
                 ve[i] <- VE.default( x[,i], y[,i], na.rm=na.rm, ... )
               }, x=sim, y=obs )    
                     
  names(ve) <- colnames(obs)
                 
  return(ve)
     
  } # 've.matrix' end
  
  
VE.data.frame <- function (sim, obs, na.rm=TRUE,...){

  sim <- as.matrix(sim)
  obs <- as.matrix(obs)
   
  VE.matrix(sim, obs, na.rm=na.rm, ...)  
     
} # 'VE.data.frame' end



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# Author: Mauricio Zambrano-Bigiarini                                          #
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# Started: 22-Mar-2013                                                         #
# Updates:                                                                     #
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VE.zoo <- function(sim, obs, na.rm=TRUE, ...){
    
    sim <- zoo::coredata(sim)
    if (is.zoo(obs)) obs <- zoo::coredata(obs)
    
    if (is.matrix(sim) | is.data.frame(sim)) {
       VE.matrix(sim, obs, na.rm=na.rm, ...)
    } else NextMethod(sim, obs, na.rm=na.rm, ...)
     
  } # 'VE.zoo' end