R/ensemble.weights.R

In BiodiversityR: Package for Community Ecology and Suitability Analysis

`ensemble.weights` <- function(
    weights=c(0.9, 0.8, 0.7, 0.5), 
    best=0, min.weight=0, exponent=1.0,
    digits=6
)
{
    names.weights <- names(weights)
    weights <- as.numeric(weights)
# also allow weights to be larger than 1, since they will be forced to sum to 1
#    if(any(weights > 1.0)) {stop("Input weights are expected to be ranged between 0 and 1")}
    names(weights) <- names.weights
#   weights should not be negative
    if (min.weight < 0) {min.weight <- 0}
    weights[weights < min.weight] <- 0
    weights[is.na(weights)] <- 0
#
# special case if all weights are zero
    if (sum(weights) == 0) {return(weights)}
#
# select best weights
# ties are handled correctly
    lw <- length(weights)
    lp <- sum(as.numeric(weights > 0))
    if (best < 1) {best <- lp}
    if (lp < best) {best <- lp}
    weights.sorted <- sort(weights, decreasing=T)   
    min.best <- weights.sorted[best]
    weights[weights < min.best] <- 0
#
# apply exponents
    weights <- weights^exponent 
#
# scaling to 1
    tot <- sum(weights)
    weights <- weights/tot
    weights <- round(weights, digits=digits)
#
    names(weights) <- names.weights
    return(weights)
}