R/iccplot.CRSM.R

In pcIRT: IRT Models for Polytomous and Continuous Item Responses

#'@rdname iccplot
#'@method iccplot CRSM

iccplot.CRSM <- function(object, items="all",...){

  pp <- seq(-30,30, by=1)
  rs <- seq(0,1, by=0.05)
  pp_rs <- expand.grid(theta = pp, resp = rs)
  func <- function(x, per, itpar){exp(x*(per-itpar) + x*(1-x)*object$disppar)}

if(is.numeric(items)){
  par(ask=TRUE)
  z2 <- sapply(items, function(l){
    resp <- sapply(1:nrow(pp_rs), function(z1){
      if(pp_rs[z1,2] == 0){
        z <- integrate(func, per=pp_rs[z1,1], itpar=object$itempar[l], lower=0.0000001, upper=0.01)$value
      }  else {
        z <- integrate(func, per=pp_rs[z1,1], itpar=object$itempar[l], lower=(pp_rs[z1,2]-0.01), upper=pp_rs[z1,2])$value
      }
      n <- integrate(func, per=pp_rs[z1,1], itpar=object$itempar[l],lower=0, upper=1)$value
      z/n
    })
    mat1 <- matrix(resp, nrow=length(pp))
    oldscale <- rs*(object$high-object$low)+object$low
    persp(pp, oldscale, mat1, xlab="theta", ylab="response scale", zlab="response probability", theta=35, phi=25, ticktype="detailed", main=names(object$itempar)[l])
  })
  par(ask=FALSE)

} else if(items=="all"){

  par(ask=TRUE)
  z2 <- sapply(1:length(object$itempar), function(l){
    resp <- sapply(1:nrow(pp_rs), function(z1){
      if(pp_rs[z1,2] == 0){
        z <- integrate(func, per=pp_rs[z1,1], itpar=object$itempar[l], lower=0.0000001, upper=0.01)$value
      }  else {
        z <- integrate(func, per=pp_rs[z1,1], itpar=object$itempar[l], lower=(pp_rs[z1,2]-0.01), upper=pp_rs[z1,2])$value
      }
      n <- integrate(func, per=pp_rs[z1,1], itpar=object$itempar[l],lower=0, upper=1)$value
      z/n
    })
    mat1 <- matrix(resp, nrow=length(pp))
    oldscale <- rs*(object$high-object$low)+object$low
    persp(pp, oldscale, mat1, xlab="theta", ylab="response scale", zlab="response probability", theta=35, phi=25, ticktype="detailed", main=names(object$itempar)[l])
  })
  par(ask=FALSE)

} else {stop("Items must be a numeric vector to choose a subset of items or must be 'all' to choose all items")

}

}