knnflex: A more flexible KNN

#'Determines the prevalence of each class
#'
#'A function which determines the prevalence or probability for each class of a
#'vector (treated as factor).
#'
#'This function treats the input vector as a factor and determines the
#'probability for each level (class) of the factor.  The order of the returned
#'probabilities is the order of the \code{\link{levels}} command, which
#'defaults to numeric or alphabetic order.
#'
#'@param x a one dimensional vector
#'@return A vector whose length is equal to the number of levels in the input.
#'The order is numerically or alphabetically increasing.  Note the factors may
#'have levels which are not present in the vector, see examples for details.
#'@author Atina Dunlap Brooks
#'@seealso \code{\link{majority}} \code{\link{factor}}
#'@keywords utilities
#'@export
#'@examples
#'
#'#calculate probbilities
#'x <- sample( c("a","b","c","d","e"), 10, replace=TRUE )
#'classprob(x)
#'#label the probabilities
#'levels(as.factor(x))
#'
#'#to see levels which aren't represnted in the vector
#'x<-as.factor(c('a','a','a','b','b','c'))
#'levels(x)
#'#now remove the 'c'
#'x<-x[1:5]
#'#but 'c' is still a level
#'levels(x)
#'#and the probability is calculated for it
#'classprob(x)
#'
`classprob` <- function(x){
    x <- as.factor(x)
    n <- nlevels(x)
    votes <- rep(0, n)
    for (i in 1:length(x)) votes[as.integer(x[i])] <- votes[as.integer(x[i])]+1
    votes/length(x)
}