R/beals.R

In vegan: Community Ecology Package

##############################################################
##  COMPUTES BEALS SMOOTHING FOR ALL SPECIES IN TABLE        #
##  This is a more complete function than the previous one   #
##  in the vegan package. The parameter values that give the #
##  equivalence are 'beals(x, NA, x, 0, include=TRUE)'       #
##                                                           #
##  'x'     matrix to be replaced by beals values            #
##  'reference' matrix to be used as source for joint occurrences#
##  'type'  sets the way to use abundance values             #
##       0 - presence/absence                                #
##       1 - abundances for conditioned probabilities        #
##       2 - abundances for weighted average                 #
##       3 - abundances for both                             #
##  'species' a column index used to compute Beals function  #
##        for a single species. The default (NA) indicates   #
##        all species.                                       #
##  'include' flag to include target species in the computation#
##############################################################
`beals` <-
    function(x, species=NA, reference=x, type=0, include=TRUE)
{
    refX <- reference
    ## this checks whether it was chosen from available options
    mode <- as.numeric(match.arg(as.character(type), c("0","1","2","3")))
    spIndex <- species
    incSp <- include
    refX <- as.matrix(refX)
    x <- as.matrix(x)
    if(mode==0 || mode ==2) refX <- ifelse(refX > 0, 1, 0)
    if(mode==0 || mode ==1) x <- ifelse(x > 0, 1, 0)
    ##Computes conditioned probabilities
    if(is.na(spIndex)){
        M <- crossprod(ifelse(refX > 0, 1, 0),refX)
        C <-diag(M)
        M <- sweep(M, 2, replace(C,C==0,1), "/")
        if(!incSp)
            for (i in 1:ncol(refX))
                M[i,i] <- 0
    } else {
        C <- colSums(refX)
        M <- crossprod(refX,ifelse(refX > 0, 1, 0)[,spIndex])
        M <- M/replace(C,C==0,1)
        if(!incSp)
            M[spIndex] <- 0
    }
    ##Average of conditioned probabilities
    S <- rowSums(x)
    if(is.na(spIndex)) {
        b <-x
        for (i in 1:nrow(x)) {
            b[i, ] <- rowSums(sweep(M, 2, x[i, ], "*"))
        }
        SM <- rep(S,ncol(x))
        if(!incSp)
            SM <- SM-x
        b <- b/replace(SM,SM==0,1)
    } else {
        b <-rowSums(sweep(x,2,M,"*"))
        if(!incSp)
            S <- S-x[,spIndex]
        b <- b/replace(S,S==0,1)
    }
    b
}