Calculating Information Gain Ratio

Question

I was searching for a piece of code that does Information Gain Ratio (IGR), in R or Python. I have found a handy R package, but it is not maintained, and has been removed from CRAN. However, I have found some old version and I took the liberty and "borrowed" critical functions. I made some changes and, also, added some new function. Algorithm expects 2x2 matrix of two cues/features and their (co)occurrence and total number of events. It gives back two IGRs, one for each cue/feature.

However, I think that it is not well optimized, and I would like to learn better way of implementing. In particular, I think there must be a way to make functions cueRE and getIGRs nicer. Below, is an example and functions.

I would appreciate any advice and comment. Many thanks!

safelog2 <- function (x) {
    if (x <= 0) return(0)
    else return(log2(x))
}

binaryMatrix <- function(m, t) {
    return(matrix(c(m[1,2], m[1,1]-m[1,2], m[2,2]-m[1,2], t-(m[1,1]+m[2,2]-m[1,2])),
        nrow=2, byrow=TRUE, dimnames=list(c(1,0),c(1,0))))
}

H <- function (p) {
    return(-(sum(p * sapply(p, safelog2))))
}

cueH <- function(m, t) {
    p1 = c(m[1,1]/t, (t-m[1,1])/t)
    p2 = c(m[2,2]/t, (t-m[2,2])/t)
    return(c(H(p1), H(p2)))
}

cueRE <- function (tbl) {
    normalize <- function(v) {
        if (sum(v) == 0) v
        else v/sum(v)
    }
    nis <- apply(t(apply(tbl, 1, normalize)), 1, H)
    return(sum(tbl * nis) / sum(tbl))
}

getIGRs <- function(m, t) {
    ent = cueH(m, t)
    rent = cueRE(binaryMatrix(m, t))
    igr1 = (ent[2] - rent) / ent[1]
    d = diag(m)
    m[1,1] = d[2]
    m[2,2] = d[1]
    ent = cueH(m, t)
    rent = cueRE(binaryMatrix(m, t))
    igr2 = (ent[2] - rent) / ent[1]
    return(c(igr1, igr2))
}

This would be used as

M <-matrix(c(20,15,15,40), nrow=2, byrow=TRUE,
    dimnames=list(c('a','b'),c('a','b')))
total <- 120

getIGRs(M, total)