R/gmc.aLR.R

In pcIRT: IRT Models for Polytomous and Continuous Item Responses

#'@rdname gmc
#'@method gmc aLR
#'@export

gmc.aLR <-
  function(object, ...){
    if(length(object$itempar) > 2) {stop("there are more than two subsamples! Only two subsamples can be plotted")}

    labs <- as.vector(t(outer(1:ncol(object$itempar[[1]]), paste0("-", 1:(nrow(object$itempar[[1]])-1)), FUN="paste0")))

    plot(as.vector(object$itempar[[1]][-nrow(object$itempar[[1]]),]), as.vector(object$itempar[[2]][-nrow(object$itempar[[2]]),]), type="p", pch=20, xlab="item par. group 1", ylab="item par. group 2", xlim=c(-ceiling(max(abs(unlist(object$itempar)))), ceiling(max(abs(unlist(object$itempar))))), ylim=c(-ceiling(max(abs(unlist(object$itempar)))),ceiling(max(abs(unlist(object$itempar))))))
    abline(0,1)
    text(as.vector(object$itempar[[1]][1:2,]), as.vector(object$itempar[[2]][1:2,]), labels=labs, pos=1)

  }