R/plot.lordif.MC.R

In lordif: Logistic Ordinal Regression Differential Item Functioning using IRT

plot.lordif.MC <-
function(x,mfrow=c(3,1),width=7,height=7,...) {
    if (class(x)!="lordif.MC") stop(paste(deparse(substitute(x))," must be of class lordif.MC"))
    nr<-x$nr
    Item<-1:dim(x$cutoff)[1]
    sysname<-Sys.info()[["sysname"]]
    if(sysname=="Windows") {
      dev.new(width=width,height=height,record=TRUE)
    } else if (sysname=="Linux") {
      dev.new(width=width,height=height)
      par(ask=TRUE)
    } else {
      dev.new(width=width,height=height)
    }
    par(mfrow=mfrow)
    par(mar=c(2,5,1,2)+0.1)
    max.chi<-max(pretty(c(x$cutoff$chi12,x$cutoff$chi13,x$cutoff$chi23)))
    plot(Item,x$cutoff$chi12,ylab=substitute(paste0("Pr(",chi[12]^2,")")),ylim=c(0,max.chi),type="b",...)
    abline(h=x$alpha,col="red")
    plot(Item,x$cutoff$chi13,ylab=substitute(paste0("Pr(",chi[13]^2,")")),ylim=c(0,max.chi),type="b",...)
    abline(h=x$alpha,col="red")
    plot(Item,x$cutoff$chi23,ylab=substitute(paste0("Pr(",chi[23]^2,")")),ylim=c(0,max.chi),type="b",...)
    abline(h=x$alpha,col="red")
    max.R2<-max(pretty(c(x$cutoff$pseudo13.McFadden,x$cutoff$pseudo13.Nagelkerke,x$cutoff$pseudo13.CoxSnell)))
    plot(Item,x$cutoff$pseudo12.McFadden,ylab=substitute(paste0(R[2]^2," - ",R[1]^2)),type="b",col="black",lty=1,ylim=c(0,max.R2))
    points(Item,x$cutoff$pseudo12.Nagelkerke,type="b",col="blue",lty=2,pch=2)
    points(Item,x$cutoff$pseudo12.CoxSnell,type="b",col="red",lty=3,pch=3)
    legend("topleft",c("McFadden","Nagelkerke","Cox & Snell"),lty=1:3,col=c("black","blue","red"),pch=1:3,bg="white")
    plot(Item,x$cutoff$pseudo13.McFadden,ylab=substitute(paste0(R[3]^2," - ",R[1]^2)),type="b",col="black",lty=1,ylim=c(0,max.R2))
    points(Item,x$cutoff$pseudo13.Nagelkerke,type="b",col="blue",lty=2,pch=2)
    points(Item,x$cutoff$pseudo13.CoxSnell,type="b",col="red",lty=3,pch=3)
    plot(Item,x$cutoff$pseudo23.McFadden,ylab=substitute(paste0(R[3]^2," - ",R[2]^2)),type="b",col="black",lty=1,ylim=c(0,max.R2))
    points(Item,x$cutoff$pseudo23.Nagelkerke,type="b",col="blue",lty=2,pch=2)
    points(Item,x$cutoff$pseudo23.CoxSnell,type="b",col="red",lty=3,pch=3)
    max.beta<-max(pretty(x$cutoff$beta12))
    plot(Item,x$cutoff$beta12,ylab=substitute(Delta(beta[1])),type="b",ylim=c(0,max.beta),...)
  }