\documentclass{article}
\usepackage[utf8]{inputenc}
\begin{document}
%\VignetteEngine{knitr::knitr}
%\VignetteIndexEntry{Data-Based Generalization (Set 3)}
\title{3: Data-Based Generalization}
\author{John H Maindonald}
\maketitle

<<setup, cache=FALSE, echo=FALSE>>=
library(knitr)
options(replace.assign=FALSE,width=72)
opts_chunk$set(fig.path='figs/infer-', cache.path='cache/infer-',
               fig.align='center', dev='pdf', fig.width=3.5,
               fig.height=3.5, fig.show='hold', par=TRUE,
               tidy=FALSE,  comment=NA)
knit_hooks$set(par=function(before, options, envir){
if (before && options$fig.show!='none') par(mar=c(4,4,1.6,.1),
              font.main=1, cex.lab=.95,cex.axis=.9,mgp=c(2,.7,0),
              tcl=-.3)
              par(options$pars)
}, crop=hook_pdfcrop)
pdf.options(pointsize=12)
oldopt <- options(digits=4)
@ %

\subsection*{Ideas and issues illustrated by the graphs in this vignette}
A central concern of data analysis is to generalize from results from
the one data set that is available for analysis to some wider
relevance. Ideas of sample and population are crucial for such
generalization.  A further important notion is that of a 
{\em sampling distribution}, 

Mechanisms for assessing predictive accuracy include the use of theory,
simulation (which extends the use of theory into areas where the calculations
may be intractable), the training/test approach, cross-validation, and 
bootstrap methods.

\paragraph{Note:}  Figures 3.15 and 3.16 show results from repeated
sampling -- simulation or bootstrap sampling.
The versions of these figures that are shown in Section \ref{fig3:show}
are for a substantially reduced number of repeat samples, relative to the
text {\em Statistically Informed Data Mining}.

\section{R Functions for Creating Chapter 3 Figures}
<<fig3_1, eval=TRUE, echo=TRUE>>=
fig3.1 <-
function (x=fCatBwt){
lattice::stripplot(jitter(x), pch='|', xlab="Weight (kg)",
                 aspect=0.25, col="black", border="gray")
}

<<fig3_2, eval=TRUE, echo=TRUE>>=
fig3.2 <-
function(x=fCatBwt){
opar <- par(mfrow=c(2,2), xpd=TRUE,
            mar=c(3.6,3.1,3.6,1.1), mgp=c(2.25, 0.5, 0))
hist(x, labels=TRUE, xlim=c(2, 3),
     xlab="Height (cm)", main="", xpd=TRUE)
title(main="A: Frequency histogram", adj=0, line=1.5, cex.main=1.05)
hist(x, labels=TRUE, xlim=c(2,3),
     xlab="Weight (kg)", main="", freq=FALSE, xpd=TRUE)
title(main="B: Density histogram", adj=0, line=1.5, cex.main=1.05)
par(xpd=FALSE)
hist(x, xlim=c(2,3), xlab="Weight (kg)",
     main="", freq=FALSE)
axis(1)
lines(density(x), xlab="Weight (kg)", col="gray40")
title(main="C: Histogram, density is overlaid", adj=0, line=1.5,
      cex.main=1.05)
plot(density(x), xlim=c(2,3), xlab="Height (cm)",
     main="", sub="", bty="l", type="l")
av <- mean(x)
sdev <- sd(x)
xval <- pretty(c(2,3), n=40)
lines(xval, dnorm(xval, mean=av, sd=sdev), lty=2, col="gray40")
title(main="D: Density curve estimate", adj=0, line=1.5, cex.main=1.05)
par(opar)
par(mfrow=c(1,1))
}

<<fig3_3, eval=TRUE, echo=TRUE>>=
fig3.3 <-
function (x=fCatBwt, plotit=TRUE){
    av <- mean(x); sdev <- sd(x); sampsize <- length(x)
    simmat <- cbind(x, matrix(rnorm(sampsize*5, mean=av, sd=sdev),
                                ncol=5))
    simdf <- as.data.frame(simmat)
    names(simdf) <- c("Source", paste("normal", 1:5, sep=""))
    simdf <- stack(simdf)
    names(simdf) <- c("height", "Sample")
    denplotSimple <- densityplot(~height, groups=Sample, data=simdf,
                                 xlab="Body weight (kg)")
    denplotn <- update(denplotSimple, scales=list(tck=0.5),
                       main=list(expression(plain("A: Simulation (Densities)")),
                       cex.title=0.9, x=0.05, just="left"),
                       par.settings=simpleTheme(lty=1:6))
    bwpltBasic <- bwplot(Sample ~ height, data=simdf,
                         xlab="Body weight (kg)",
                         auto.key=list(columns=3))
    bwplotn <- update(bwpltBasic, scales=list(tck=0.5),
                      main=list(expression(plain("B: Simulation (Boxplots)")), 
                                cex.title=0.9, x=0.05, just="left"))
    if(plotit){
        print(denplotn, position=c(0,0,0.5,1))
        print(bwplotn, position=c(0.5,0,1,1),newpage=FALSE)
    }
    invisible(list(denplotn, bwplotn))
}
@ %

<<fig3_4, eval=TRUE, echo=TRUE>>=
fig3.4 <-
function (x=fCatBwt, plotit=TRUE)
{
    sampsize <- length(x)
    bootmat <- cbind(x, matrix(0, ncol=5, nrow=sampsize))
    for(i in 2:6) bootmat[,i] <- sample(x, replace=TRUE)
    colnames(bootmat) <- c("Source", paste("normal", 1:5, sep=""))
    bootdf <- stack(as.data.frame(bootmat))
    names(bootdf) <- c("height", "Sample")
    denplotSimple <- densityplot(~ height, groups=Sample, data=bootdf,
                                 xlab="Body weight (kg)")
    legendA <- expression(plain("A: Bootstrap (Densities)"))
    denplot <- update(denplotSimple, scales=list(tck=0.5),
                      main=list(legendA, x=0.05, just="left"), cex.title=0.9,
                      par.settings=simpleTheme(lty=1:6))
    bwpltBasic <- bwplot(Sample ~ height, data=bootdf,
                         xlab="Body weight (kg)",
                         auto.key=list(columns=3))
    legendB <- expression(plain("B: Bootstrap (Boxplots)"))
    bwplot <- update(bwpltBasic, scales=list(tck=0.5),
                     main=list(legendB, x=0.05, just="left"), cex.title=0.9)
    if(plotit){
        print(denplot, position=c(0,0,0.5,1))
        print(bwplot, position=c(0.5,0,1,1),newpage=FALSE)
    }
    invisible(list(denplot, bwplot))
}
@ %

<<fig3_5, eval=TRUE, echo=TRUE>>=
fig3.5 <-
function ()
{
    opar <- par(mgp=c(2,.75,0), mfrow=c(1,2))
    curve(dnorm(x), from = -3, to = 3,
          ylab=expression("dnorm("*italic(x)*")"),
          xlab=expression("Normal deviate "*italic(x)))
    curve(pnorm(x), from = -3, to = 3,
          ylab=expression("pnorm("*italic(x)*")"),
          xlab=expression("Normal deviate "*italic(x)))
    par(opar)
}
@ %

<<fig3_6, eval=TRUE, echo=TRUE>>=
fig3.6 <-
function (){
    heights <- na.omit(subset(survey, Sex=="Female")$Height)
    plot(density(heights), bty="l", main="",
         cex.axis=1.15, cex.lab=1.15)
    av <- mean(heights); sdev <- sd(heights)
    abline(v=c(av-sdev, av, av+sdev), col="gray", lty=c(2,1,2))
    ## Show fitted normal curve
    xval <- pretty(heights, n=40)
    normal_den <- dnorm(xval, mean=av, sd=sdev)
    lines(xval, normal_den, col="gray40", lty=2)
    ytop <- par()$usr[4]-0.25*par()$cxy[2]
    text(c(av-sdev, av+sdev), ytop,
         labels=c("mean-SD","mean+SD"), col="gray40", xpd=TRUE)
}
@ %

<<fig3_7, eval=TRUE, echo=TRUE>>=
fig3.7 <-
function (wts=fCatBwt){
    opar <- par(pty="s")
    qqnorm(wts)
    par(opar)
}
@ %

<<fig3_8, eval=TRUE, echo=TRUE>>=
fig3.8 <-
function (wts=fCatBwt)
{
    opar <- par(mfrow=c(1,2), mar=c(2.1, 3.6, 3.6,2.6),
                mgp=c(2.25, 0.5,0))
    av <- numeric(1000)
    for (i in 1:1000)
        av[i] <- mean(rnorm(47, mean=2.36, sd=0.27))
    avdens <- density(av)
    xval <- pretty(c(2.36-3*0.27, 2.36+3*0.27), 50)
    den <- dnorm(xval, mean=2.36, sd=0.27)
    plot(xval, den, type="l", xlab="",  xlim=c(1.5, 3.75),
         ylab="Density", ylim=c(0,max(avdens$y)),
         col="gray", lwd=2, lty=2)
    lines(avdens)
    mtext(side=3, line=0.75, "A: Simulation (from a normal distribution)",
          adj=0)
    legend("bottomright", 
           legend=c("Source", "Sampling\ndistribution\nof mean"),
           col=c("gray", "black"), lty=c(2,1), lwd=c(2,1), bty="n", 
           y.intersp=0.75, inset=c(0,0.2),
           cex=0.8)
    av <- numeric(1000)
    for (i in 1:1000)
        av[i] <- mean(sample(wts, size=length(wts), replace=TRUE))
    avdens <- density(av)
    plot(density(wts), ylim=c(0, max(avdens$y)),
         xlab="", ylab="Density", xlim=c(1.5, 3.75),       
         col="gray", lwd=2, lty=2, main="")
    lines(avdens)
    mtext(side=3, line=0.75, 
          "B: Bootstrap samples (resample sample)", adj=0)
    legend("bottomright", 
           legend=c("Source",
                      "Sampling\ndistribution\nof mean"),
           col=c("gray", "black"), lty=c(2,1), lwd=c(2,1), bty="n",
           y.intersp=0.75, inset=c(0,0.2),
           cex=0.8)
    par(opar)
    par(mfrow=c(1,1))
}
@ %

<<fig3_9, eval=TRUE, echo=TRUE>>=
fig3.9 <-
function ()
{
    xleft <- 0:3; xrt <- 1:4
    ybot <- rep(0,4); ytop <- rep(1,4) - 0.05
    opar <- par(mar=rep(0.1,4))
    plot(c(0,5), c(-1,4), xlab="", ylab="", axes=F, type="n")
    for(i in 0:3){
        i1 <- i+1
        rect(xleft, ybot+i, xrt, ytop+i)
        xli <- xleft[i+1]; xri <- xrt[i+1];
        yboti <- (ybot+i)[i+1]; ytopi <- (ytop+i)[i+1]
        rect(xli, yboti, xri, ytopi, col="gray80")
        text(0.5*(xli+xri), 0.5*(yboti+ytopi), "TEST")
        text(0.5*(xleft[-i1]+xrt[-i1]), 0.5*(ybot[-i1]+ytop[-i1])+i, "Training")
        text(4+strwidth("TE"), i+0.475, paste("Fold", i1), adj=0)
}
}
@ %

<<fig3_10, eval=TRUE, echo=TRUE>>=
fig3.10 <-
function (dset=cuckoos, plotit=TRUE)
{
    parset1 <- lattice::simpleTheme(pch=1:6, alpha=0.8)
    plt1 <- lattice::xyplot(length ~ breadth, groups=species, data=dset,
                   par.settings=parset1, aspect=1,
                   scales=list(tck=0.5),
                   auto.key=list(columns=2, alpha=1),
                   main=grid::textGrob("A:", x=unit(.025, "npc"),
                   y = unit(.25, "npc"), just="left",
                   gp=gpar(cex=1))
                   )
    Species <- factor(c(rep("other", 5), "wren")[unclass(cuckoos$species)])
    parset2 <- lattice::simpleTheme(pch=c(0,6), alpha=0.8,
                           col=trellis.par.get()$superpose.symbol$col[c(7,6)])
    plt2 <- lattice::xyplot(length ~ breadth, groups=Species, data=dset,
                   par.settings=parset2,
                   aspect=1, ylab="", scales=list(tck=0.25),
                   auto.key=list(columns=1, alpha=1),
                   main=grid::textGrob("B:", x=unit(.05, "npc"),
                   y = unit(.25, "npc"), just="left",
                   gp=grid::gpar(cex=1))
                   )
    plt2 <- update(plt2,
                   par.settings=list(layout.heights=list(key.top=1.5)))
    if(plotit){
        print(plt1, position=c(0,0,0.515,1))
        print(plt2, position=c(0.485,0,1,1), newpage=FALSE)
    }
    invisible(list(plt1, plt2))
}
@ %

<<fig3_11, eval=TRUE, echo=TRUE>>=
fig3.11 <-
function (dset=cuckoos)
{
    parset <- list(dot.symbol=list(pch=1, alpha=0.6))
    dotwren <- dotplot(species %in% "wren" ~ length, data=dset,
                       scales=list(y=list(labels=c("Other", "Wren"))),
                       par.settings=parset, xlab="Length (mm)")
    dotwren
}
@ %

<<fig3_12, eval=TRUE, echo=TRUE>>=
fig3.12 <-
function(dset=cuckoos)
{
    avdiff <- numeric(100)
    for(i in 1:100){
        avs <- with(dset, sapply(split(length, species %in% "wren"),
                                    function(x)mean(sample(x, replace=TRUE))))
        avdiff[i] <- avs[1] - avs[2]  # FALSE (non-wren) minus TRUE (wren)
    }
    xtxt <- paste("Means of bootstrap samples of length difference,\n",
                  "non-wren - wren (mm)")
    dotdiff <- dotplot(~ avdiff, xlab=xtxt,
                       par.settings=list(dot.symbol=list(pch=1, alpha=0.6)))
    dotdiff
}
@ %

<<fig3_13, eval=TRUE, echo=TRUE>>=
fig3.13 <-
function (dset=mcats)
{
    xyplot(Hwt ~ Bwt, data=dset,
           type=c("p","r"))
}
@ %

<<fig3_14, eval=TRUE, echo=TRUE>>=
fig3.14 <-
function(dset=mcats)
{
    mcats.lm <- lm(Hwt ~ Bwt, data=dset)
    res <- resid(mcats.lm)
    plot(density(res), main="")
    rug(res, col="gray")
}
@ %

<<fig3_15, eval=TRUE, echo=TRUE>>=
fig3.15 <-
function(dset=mcats, nrepeats=100)
{
    bootmat <- bootreg(formula = Hwt ~ Bwt,
                       data = dset,
                       nboot = nrepeats)
    bootdf <- as.data.frame(bootmat)
    names(bootdf) <- c("Intercept","Slope")
    colr <- adjustcolor(rep("black",3),
                        alpha.f=0.25)
    scatterplot(Slope ~ Intercept, col=colr,
                data=bootdf, boxplots="xy",
                reg.line=NA, smooth=FALSE)
}
@ %

<<fig3_16, eval=TRUE, echo=TRUE>>=
fig3.16 <-
function (dset=mcats, plotit=TRUE, nrepeats=100)
{
    bootmat <- bootreg(formula = Hwt ~ Bwt,
                       data = dset[-97, ],
                       nboot = nrepeats)
    bootdf0 <- as.data.frame(bootmat)
    names(bootdf0) <- c("Intercept","Slope")
    gphA <- xyplot(Slope ~ Intercept, data=bootdf0, alpha=0.25,
                   main=paste("A:", nrepeats, "bootstrap samples"),
                   cex.title=1.1)
        simmat <- simreg(formula = Hwt ~ Bwt,
                         data=dset[-97, ], nsim=nrepeats)
    simdf <- as.data.frame(simmat)
    names(simdf) <- c("Intercept","Slope")
    gphB <- xyplot(Slope ~ Intercept, data=simdf, alpha=0.25,
                   main=paste("B:", nrepeats, "simulations"),
                   cex.title=1.1)
    if(plotit){
        print(gphA, position=c(0,0,0.515,1))
        print(gphB, position=c(0.485,0,1,1), newpage=FALSE)
    }
    invisible(list(gphA, gphB))
}
@ %

\section{Show the Figures}\label{fig3:show}

<<fig3-pkgs, warning=FALSE, message=FALSE>>=
pkgs <- c("lattice","DAAG","gamclass","MASS","car","grid")
z <- sapply(pkgs, require, character.only=TRUE, 
            warn.conflicts=FALSE, quietly=TRUE)
if(any(!z)){
  notAvail <- paste(names(z)[!z], collapse=", ")
  print(paste("The following packages should be installed:", notAvail))
}
@ %

<<get-data, eval=TRUE>>=
msg <- "Data object 'cats', from 'MASS', may not be available"
if(!requireNamespace("MASS"))print(msg) else {
  mcats <- subset(MASS::cats, Sex=="M")
  fcats <- subset(MASS::cats, Sex=="F")
  fCatBwt <- na.omit(fcats[, "Bwt"])
}
if(!exists("cuckoos")){
        msg <- "Cannot find either 'cuckoos' or 'DAAG::cuckoos',"
if(requireNamespace("DAAG"))cuckoos <- DAAG::cuckoos else 
          print(msg)
      }    
@ %

<<fig3_1x, eval=TRUE, echo=TRUE, fig.width=4.5, fig.height=2.5, out.width="0.75\\textwidth">>=
if(exists('fCatBwt'))fig3.1() else
    print("Object 'fCatBwt' is not available; get from 'MASS::cats'")
@ %

<<fig3_2x, eval=TRUE, echo=TRUE, fig.width=5.5, fig.height=5.5, out.width="0.8\\textwidth">>=
if(exists('fCatBwt'))fig3.2() else
    print("Object 'fCatBwt' is not available; get from 'MASS::cats'")
@ %

<<fig3_3x, eval=TRUE, echo=TRUE, fig.width=6, fig.height=3, out.width="0.8\\textwidth">>=
if(exists('fCatBwt'))fig3.3() else
    print("Object 'fCatBwt' is not available; get from 'MASS::cats'")
@ %

<<fig3_4x, eval=TRUE, echo=TRUE, fig.width=6, fig.height=3, out.width="0.8\\textwidth">>=
if(exists('fCatBwt'))fig3.4() else
    print("Object 'fCatBwt' is not available; get from 'MASS::cats'")
@ %

<<fig3_5x, eval=TRUE, echo=TRUE, fig.width=6, fig.height=3.25, out.width="0.8\\textwidth">>=
fig3.5()
@ %

<<fig3_6x, eval=TRUE, echo=TRUE, fig.width=4.5, fig.height=3.5, out.width="0.55\\textwidth">>=
fig3.6()
@ %

<<fig3_7x, eval=TRUE, echo=TRUE, out.width="0.5\\textwidth">>=
if(exists("fCatBwt"))fig3.7() else
    print("Object 'fCatBwt' was not found; get from 'MASS::cats'")
@ %

<<fig3_8x, eval=TRUE, echo=TRUE, fig.width=8, fig.height=3.5, out.width="0.98\\textwidth">>=
if(exists("fCatBwt"))fig3.8() else
    print("Object 'fCatBwt' was not found; get from 'MASS::cats'")
@ %

<<fig3_9x, eval=TRUE, echo=TRUE, fig.width=4, fig.height=3, out.width="0.6\\textwidth">>=
fig3.9()
@ %

<<fig3_10x, eval=TRUE, echo=TRUE, fig.width=6, fig.height=3.5, out.width="0.97\\textwidth">>=
if(exists("cuckoos"))fig3.10() else
    print("Object 'cuckoos' was not found; get 'DAAG::cuckoos'")  
@ %

<<fig3_11x, eval=TRUE, echo=TRUE, fig.width=4.5, fig.height=2.5, out.width="0.6\\textwidth">>=
if(exists("cuckoos"))fig3.11() else
    print("Object 'cuckoos' was not found; get 'DAAG::cuckoos'")  
@ %

<<fig3_12x, eval=TRUE, echo=TRUE, fig.width=4.5, fig.height=2.5, out.width="0.6\\textwidth">>=
if(exists("cuckoos"))fig3.12() else
    print("Object 'cuckoos' was not found; get 'DAAG::cuckoos'")  
@ %

<<fig3_13x, eval=TRUE, echo=TRUE, fig.width=4, fig.height=4, out.width="0.55\\textwidth">>=
if(exists('mcats'))fig3.13() else
    print("Object 'mcats' was not found; subset from 'MASS::cats'")
@ %

<<fig3_14x, eval=TRUE, echo=TRUE, fig.width=3.5, fig.height=3, out.width="0.5\\textwidth">>=
if(exists('mcats'))fig3.14() else
    print("Object 'mcats' was not found; subset from 'MASS::cats'")
@ %

<<fig3_15x, eval=TRUE, echo=TRUE, out.width="0.6\\textwidth">>=
if(!require(car)){
    print("Figure 3.15 requires the 'car' package")
    return("The 'car' package needs to be installed.")
}
if(exists("mcats"))fig3.15(nrepeats=100) else
    print("Object 'mcats' was not found; subset from 'MASS::cats'")
@ %

<<fig3_16x, eval=TRUE, echo=TRUE, fig.width=6.5, fig.height=3.25, out.width="0.97\\textwidth">>=
if(exists('mcats'))fig3.16() else
    print("Object 'mcats' was not found; subset from 'MASS::cats'")
@ %

\end{document}