##' @title Fisher's Z test for comparing two correllation coefficients.
##'
##' @description None yet.
##'
##' @details
##' Test whether two correlation coefficients are statistically different using the difference
##' between Fisher's Z transforms.
##'
##' Method cribbed from:
##' \enumerate{
##' \item \url{http://www.fon.hum.uva.nl/Service/Statistics/Two_Correlations.html}
##' \item \url{http://ftp.sas.com/techsup/download/stat/compcorr.html}
##' }
##' Implemented in R by me.
##'
##' @param n1 n for correlation 1.
##' @param r1 r for correlation 1.
##' @param n2 n for correlation 2.
##' @param r2 r for correlation 2.
##' @return list containing diff(Z1, Z2) and pval for difference.
##' @author Dave Braze \email{davebraze@@gmail.com}
##' @import stats
##' @export
compCorr <- function(n1, r1, n2, r2){
## Fisher Z-transforms
zf1 <- 0.5*log((1 + r1)/(1 - r1))
zf2 <- 0.5*log((1 + r2)/(1 - r2))
## difference
dz <- (zf1 - zf2)/sqrt(1/(n1 - 3) + (1/(n2 - 3)))
## p-value
pv <- 2*(1 - stats::pnorm(abs(dz)))
retval <- list(diff=dz, pval=pv)
retval
}
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