R/agree_aicken.R

In immer: Item Response Models for Multiple Ratings

## File Name: agree_aicken.R
## File Version: 0.09

#################################
# algorithm for Aicken's statistic
agree_aicken <- function( PAk, PBk, Pa )
{
    PAH <- PAk
    PBH <- PBk
    alpha <- .5
    ii <- 0
    conv <- FALSE
    maxiter <- 100
    globconv <- 1E-5
    while( ! conv){
        alpha0 <- alpha
        pet <- sum( PAH * PBH )
        alpha <- ( Pa - pet ) / ( 1 - pet )
        PAH <- PAk / (  ( 1 - alpha )  + alpha * PBH  / pet )
        PBH <- PBk / (  ( 1 - alpha )  + alpha * PAH  / pet )
        ii <- ii+1
        diff_conv <- abs( alpha0 - alpha )
        if (diff_conv < globconv){ conv <- TRUE }
        if (ii==maxiter ){ conv <- TRUE }
    }
    # chance agreement
    Pe <- pet
    # output
    res <- list( "alpha"=alpha, "PAH"=PAH,
                    "PBH"=PBH, "Pe"=Pe )
    return(res)
}