R/FA2.R

In FSMUMI: Imputation of Time Series Based on Fuzzy Logic

#' @title FA2
#' @author Thi-Thu-Hong Phan, Andre Bigand, Emilie Poisson-Caillault
#' @description Calculate the FA2 between two univariate signals Y (imputed values) and X (true values).
#' @details
#' This function returns the FA2 value which corresponds to the percentage of pairs of values (\eqn{x_{i}, y_{i}}) satisfying the condition \eqn{0,5 <= (y_{i}/x_{i}) <= 2}.
#' FA2 is close to 1, the imputation model is more accurate.
#' Both vectors Y and X must be of equal length, on the contrary an error will be displayed.
#' In both input vectors, eventual NA will be exluded with a warning diplayed.
#' @param Y vector of imputed values
#' @param X vector of true values
#' @param verbose if TRUE, print advice about the quality of the model
#' @examples
#' data(dataFSMUMI)
#' X <- dataFSMUMI[, 1] ; Y <- dataFSMUMI[, 2]
#' compute.fa2(Y,X)
#' compute.fa2(Y,X, verbose = TRUE)
#' 
#' # By definition, if pairs of true and imputed values are zero,
#' # FA2 corresponding to this pair of values equals 1.
#' X[1] <- 0
#' Y[1] <- 0
#' compute.fa2(Y,X)

compute.fa2<-function(Y, X,verbose=F){
  
  Xtemp <- X
  Ytemp <- Y
  
  if(length(Y)!=length(X)){stop("Input vectors are of different length !!!")}
  
  lengthNAX <- sum(is.na(X)) # Number of NA values
  if(lengthNAX > 0){warning(paste("Vector of true values contains ", lengthNAX, " NA !!! NA excluded", sep = ""))}
  lengthNAY <- sum(is.na(Y)) # Number of NA values
  if(lengthNAY > 0){warning(paste("Vector of imputed values contains ", lengthNAY, " NA !!! NA excluded", sep = ""))}
  
  Xtemp <- X[which(!is.na(X)&!is.na(Y))] # Removing NA
  Ytemp <- Y[which(!is.na(X)&!is.na(Y))] # Removing NA
  
  id0XY <- which(X==0&Y==0) # Identify pairs of XY values equal to 0
  Xtemp[id0XY] <- 1
  Ytemp[id0XY] <- 1
  
  ratio <- (Ytemp/Xtemp)
  fraction <- ratio[ratio>=0.5 & ratio<=2]
  FA2 <- length(fraction)/length(ratio)
  if (verbose){
    if(FA2>0.8) {print(" Good model")
    }else{print("Important number of different points")}
  }
  out<-FA2
  return(out)
}