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,BW=FALSE,...) {
    if (!inherits(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)
    # }
    if (BW) cols=c("black","dark gray","gray") else cols=c("black","blue","red")
    old.par<-par(no.readonly=TRUE)
    on.exit(par(old.par))
    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=expression("Pr("~chi[12]^2~")"),ylim=c(0,max.chi),type="b",...)
    abline(h=x$alpha,col=cols[3])
    plot(Item,x$cutoff$chi13,ylab=expression("Pr("~chi[13]^2~")"),ylim=c(0,max.chi),type="b",...)
    abline(h=x$alpha,col=cols[3])
    plot(Item,x$cutoff$chi23,ylab=expression("Pr("~chi[23]^2~")"),ylim=c(0,max.chi),type="b",...)
    abline(h=x$alpha,col=cols[3])
    max.R2<-max(pretty(c(x$cutoff$pseudo13.McFadden,x$cutoff$pseudo13.Nagelkerke,x$cutoff$pseudo13.CoxSnell)))
    plot(Item,x$cutoff$pseudo12.McFadden,ylab=expression(R[2]^2~-~R[1]^2),type="b",col=cols[1],lty=1,ylim=c(0,max.R2))
    points(Item,x$cutoff$pseudo12.Nagelkerke,type="b",col=cols[2],lty=2,pch=2)
    points(Item,x$cutoff$pseudo12.CoxSnell,type="b",col=cols[3],lty=3,pch=3)
    legend("topleft",c("McFadden","Nagelkerke","Cox & Snell"),lty=1:3,col=cols,pch=1:3,bg="white")
    plot(Item,x$cutoff$pseudo13.McFadden,ylab=expression(R[3]^2~-~R[1]^2),type="b",col=cols[1],lty=1,ylim=c(0,max.R2))
    points(Item,x$cutoff$pseudo13.Nagelkerke,type="b",col=cols[2],lty=2,pch=2)
    points(Item,x$cutoff$pseudo13.CoxSnell,type="b",col=cols[3],lty=3,pch=3)
    plot(Item,x$cutoff$pseudo23.McFadden,ylab=expression(R[3]^2~-~R[2]^2),type="b",col=cols[1],lty=1,ylim=c(0,max.R2))
    points(Item,x$cutoff$pseudo23.Nagelkerke,type="b",col=cols[2],lty=2,pch=2)
    points(Item,x$cutoff$pseudo23.CoxSnell,type="b",col=cols[3],lty=3,pch=3)
    max.beta<-max(pretty(x$cutoff$beta12))
    plot(Item,x$cutoff$beta12,ylab=expression(Delta(beta[1])),type="b",ylim=c(0,max.beta),...)
    invisible()
  }