R/describing.R

In DavideMassidda/testing: Psychometric Testing

# Indice di entropia (variabilita' per dati nominali)
entropy <- function(x, base = exp(1), inverse = FALSE)
{
    f <- table(x)
    p <- f/sum(f)
    ln.p <- log(p,base=base)
    ln.p[ln.p == (-Inf)] <- 0
    H = -sum(p * ln.p)
    if(inverse)
        H <- base^H
    return(H)
}

# Calcola le frequenze considerando tutto lo spettro di valori nell'intervallo
integer_counts <- function(x,x.min=min(x),x.max=max(x),perc=FALSE,na.keep=TRUE)
{
    n <- length(x)
    # Conversion to numeric
    if(is.factor(x))
        x <- as.character(x)
    x <- as.integer(x)
    # Missing data management
    na.check <- is.na(x)
    if(!na.keep)
        n <- n-sum(na.check)
    x <- x[!na.check]
    # Frequency calculation
    span <- x.min:x.max
    freq <- sapply(span, function(v) sum(x==v))
    # Conversion to percentages
    if(perc)
        freq <- freq/n*100
    # Preparation to output
    names(freq) <- span
    return(freq)
}