Adjust normTail function so it is possible to add a normal distributi…

…on to an existing plot

.gitignore

@@ -15,3 +15,4 @@ main.toc
 *gitignore~
 *.Rapp.history
 archive/*
+*.DS_Store

openintro/R/normTail.R

@@ -17,6 +17,7 @@
                        xLab = c('number', 'symbol'),
                        cex.axis = 1,
                        xAxisIncr = 1,
+                       add = FALSE,
                        ...) {
   if (is.null(xlim)[1]) {
     xlim <- m + c(-1, 1) * 3.5 * s
@@ -29,15 +30,19 @@
   if (is.null(ylim)[1]) {
     ylim <- range(c(0, y))
   }
-  plot(x, y,
-       type = 'l',
-       xlim = xlim,
-       ylim = ylim,
-       xlab = xlab,
-       ylab = ylab,
-       axes = FALSE,
-       col = curveColor,
-       ...)
+  if (add) {
+    lines(x, y, col = curveColor, ...)
+  } else {
+    plot(x, y,
+         type = 'l',
+         xlim = xlim,
+         ylim = ylim,
+         xlab = xlab,
+         ylab = ylab,
+         axes = FALSE,
+         col = curveColor,
+         ...)
+  }
   if (!is.null(L[1])) {
     these <- (x <= L)
     X <- c(x[these][1], x[these], rev(x[these])[1])
@@ -57,7 +62,7 @@
     polygon(X, Y, border = border, col = col)
   }
 
-  if (axes == 1 || axes > 2) {
+  if (!add && (axes == 1 || axes > 2)) {
     if (xLab[1] == 'symbol') {
       xAt  <- m + (-3:3) * s
       xLab <- expression(mu - 3 * sigma,
@@ -77,12 +82,12 @@
       xLab <- round(xAt, digits = digits)
     }
   }
-  if (axes > 2) {
+  if (!add && axes > 2) {
     axis(1, at = xAt, labels = xLab, cex.axis = cex.axis)
     buildAxis(2, c(y, 0), n = 3, nMax = 3, cex.axis = cex.axis)
-  } else if (axes > 1) {
+  } else if (!add && axes > 1) {
     buildAxis(2, c(y, 0), n = 3, nMax = 3, cex.axis = cex.axis)
-  } else if (axes > 0) {
+  } else if (!add && axes > 0) {
     axis(1, at = xAt, labels = xLab, cex.axis = cex.axis)
   }
   abline(h = 0)

openintro/man/normTail.Rd

@@ -1,48 +1,67 @@
 \name{normTail}
 \alias{normTail}
-\title{ Normal distribution tails }
-\description{ Produce a normal (or t) distribution and shaded tail. }
+\title{Normal distribution tails}
+\description{Produce a normal (or t) distribution and shaded tail.}
 \usage{
 normTail(m = 0, s = 1, L = NULL, U = NULL, M = NULL, df=1000,
 	curveColor=1, border = 1, col = "#CCCCCC", xlim = NULL,
 	ylim=NULL, xlab = "", ylab = "", digits = 2, axes = 1,
 	detail = 999, xLab = c("number", "symbol"), cex.axis = 1,
-	xAxisIncr=1, ...)
+	xAxisIncr = 1, add = FALSE, ...)
 }
 \arguments{
   \item{m}{ Numerical value for the distribution mean. }
   \item{s}{ Numerical value for the distribution standard deviation. }
-  \item{L}{ Numerical value representing the cutoff for a shaded lower tail. }
-  \item{U}{ Numerical value representing the cutoff for a shaded upper tail. }
-  \item{M}{ Numerical value representing the cutoff for a shaded central region. }
-  \item{df}{ Numerical value describing the degrees of freedom. Default is \code{1000}, which results in a nearly normal distribution. Small values may be useful to emphasize small tails. }
+  \item{L}{ Numerical value representing the cutoff for a shaded
+      lower tail. }
+  \item{U}{ Numerical value representing the cutoff for a shaded
+      upper tail. }
+  \item{M}{ Numerical value representing the cutoff for a shaded
+      central region. }
+  \item{df}{ Numerical value describing the degrees of freedom.
+      Default is \code{1000}, which results in a nearly normal
+      distribution. Small values may be useful to emphasize
+      small tails. }
   \item{curveColor}{ The color for the distribution curve. }
   \item{border}{ The color for the border of the shaded area. }
   \item{col}{ The color for filling the shaded area. }
   \item{xlim}{ Limits for the x axis. }
   \item{ylim}{ Limits for the y axis. }
   \item{xlab}{ A title for the x axis. }
   \item{ylab}{ A title for the y axis. }
-  \item{digits}{ The maximum number of digits past the decimal to use in axes values. }
-  \item{axes}{ A numeric value denoting whether to draw both axes (\code{3}), only the vertical axes (\code{2}), only the horizontal axes (\code{1}, the default), or no axes (\code{0}). }
-  \item{detail}{ A number describing the number of points to use in drawing the normal curve. Smaller values correspond to a less smooth curve but reduced memory usage in the final file. }
-  \item{xLab}{ If \code{"number"}, then the axis is drawn at the mean, and every standard deviation out until the third standard deviation. If \code{"symbol"}, then Greek letters are used for standard deviations from three standard deviations from the mean. }
-  \item{cex.axis}{ Numerical value controlling the size of the axis labels. }
-  \item{xAxisIncr}{ A number describing how often axis labels are placed, scaled by standard deviations. This argument is ignored if \code{xLab="symbol"}. }
+  \item{digits}{ The maximum number of digits past the decimal
+      to use in axes values. }
+  \item{axes}{ A numeric value denoting whether to draw both axes
+      (\code{3}), only the vertical axes (\code{2}), only the
+      horizontal axes (\code{1}, the default), or no axes
+      (\code{0}). }
+  \item{detail}{ A number describing the number of points to
+      use in drawing the normal curve. Smaller values correspond
+      to a less smooth curve but reduced memory usage in the
+      final file. }
+  \item{xLab}{ If \code{"number"}, then the axis is drawn at
+      the mean, and every standard deviation out until the third
+      standard deviation. If \code{"symbol"}, then Greek letters
+      are used for standard deviations from three standard
+      deviations from the mean. }
+  \item{cex.axis}{ Numerical value controlling the size of the
+      axis labels. }
+  \item{xAxisIncr}{ A number describing how often axis labels are
+      placed, scaled by standard deviations. This argument is ignored
+      if \code{xLab = "symbol"}. }
+  \item{add}{Boolean indicating whether to add this normal curve to
+      the existing plot.}
   \item{\dots}{ Additional arguments to \code{plot}. }
 }
-\author{ DM Diez }
-\seealso{
-\code{\link{buildAxis}}
-}
+\author{David Diez}
+\seealso{\code{\link{buildAxis}}}
 \examples{
-par(mfrow=c(2,3), mar=c(3,3,1,1))
-normTail(3,2,5)
-normTail(3,2,1, xLab='symbol')
-normTail(3,2,M=1:2, xLab='symbol', cex.axis=0.8)
-normTail(3,2,U=5,axes=FALSE)
-normTail(L=-1, U=2, M=c(0,1), axes=3, xAxisIncr=2)
-normTail(L=-1, U=2, M=c(0,1), xLab='symbol', cex.axis=0.8, xAxisIncr=2)
+par(mfrow = c(2, 3), mar = c(3, 3, 1, 1))
+normTail(3, 2, 5)
+normTail(3, 2, 1, xLab = 'symbol')
+normTail(3, 2, M = 1:2, xLab = 'symbol', cex.axis = 0.8)
+normTail(3, 2, U = 5, axes = FALSE)
+normTail(L = -1, U = 2, M = c(0, 1), axes = 3, xAxisIncr = 2)
+normTail(L = -1, U = 2, M = c(0, 1),
+         xLab = 'symbol', cex.axis = 0.8, xAxisIncr = 2)
 }
-\keyword{ normal }
-\keyword{ tail }