The R Project SVN R

\name{plotmath}
\alias{plotmath}
\title{Mathematical Annotation in R}
\description{
  If the \code{text} argument to one of the text-drawing functions
  (\code{\link{text}}, \code{\link{mtext}}, \code{\link{axis}}) in \R
  is an expression, the argument is interpreted as a mathematical
  expression and the output will be formatted according to TeX-like
  rules.
}
\details{
  A mathematical expression must obey the normal rules of syntax for any
  \R expression, but it is interpreted according to very different rules
  than for normal \R expressions.

  It is possible to produce many different mathematical symbols, generate
  sub- or superscripts, produce fractions, etc.

  The output from \code{example(plotmath)} includes several tables which
  show the available features.  In these tables, the columns of grey text
  show sample \R expressions, and the columns of black text show the
  resulting output.
}
\references{Murrell, P. and Ihaka, R. \emph{An approach to providing
  mathematical annotation in plots}, Journal of Computational and Graphical
  Statistics (In Press).}
\seealso{
  \code{\link{axis}},
  \code{\link{mtext}},
  \code{\link{text}},
  \code{\link{title}}
}
\examples{
x <- seq(-4, 4, len = 101)
y <- cbind(sin(x), cos(x))
matplot(x, y, type = "l", xaxt = "n",
        main = expression(paste(plain(sin) * phi, "  and  ",
                                plain(cos) * phi)),
        ylab = expression("sin" * phi, "cos" * phi), # only 1st is taken
        xlab = expression(paste("Phase Angle ", phi)),
        col.main = "blue")
axis(1, at = c(-pi, -pi/2, 0, pi/2, pi),
     lab = expression(-pi, -pi/2, 0, pi/2, pi))

plot(1:10, 1:10)
text(4, 9, expression(hat(beta) == (X^t * X)^{-1} * X^t * y))
text(4, 8.4, "expression(hat(beta) == (X^t * X)^{-1} * X^t * y)",
     cex = .8)
text(4, 7, expression(bar(x) == sum(frac(x[i], n), i==1, n)))
text(4, 6.4, "expression(bar(x) == sum(frac(x[i], n), i==1, n))",
     cex = .8)
text(8, 5, expression(paste(frac(1, sigma*sqrt(2*pi)), " ",
                            plain(e)^{frac(-(x-mu)^2, 2*sigma^2)})),
     cex= 1.2)

######
# create tables of mathematical annotation functionality
######
make.table <- function(nr, nc) {
    savepar <- par(mar=rep(0, 4), pty="s")
    plot(c(0, nc*2 + 1), c(0, -(nr + 1)), 
         type="n", xlab="", ylab="", axes=F)
    savepar
}

get.r <- function(i, nr) {
    i \%\% nr + 1
}

get.c <- function(i, nr) {
    i \%/\% nr + 1
}

draw.title.cell <- function(title, i, nr) {
    r <- get.r(i, nr)
    c <- get.c(i, nr)
    text(2*c - .5, -r, title)
    rect((2*(c - 1) + .5), -(r - .5), (2*c + .5), -(r + .5))
}

draw.plotmath.cell <- function(expr, i, nr, string = NULL) {
    r <- get.r(i, nr)
    c <- get.c(i, nr)
    if (is.null(string)) {
        string <- deparse(expr)
    string <- substr(string, 12, nchar(string) - 1)
    }
    text((2*(c - 1) + 1), -r, string, col="grey")
    text((2*c), -r, expr, adj=c(.5,.5))
    rect((2*(c - 1) + .5), -(r - .5), (2*c + .5), -(r + .5), border="grey")
}

nr <- 20
nc <- 2
oldpar <- make.table(nr, nc)
i <- 0
draw.title.cell("Arithmetic Operators", i, nr); i <- i + 1
draw.plotmath.cell(expression(x + y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x - y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x * y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x / y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%+-\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%/\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%*\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(-x), i, nr); i <- i + 1
draw.plotmath.cell(expression(+x), i, nr); i <- i + 1
draw.title.cell("Sub/Superscripts", i, nr); i <- i + 1
draw.plotmath.cell(expression(x[i]), i, nr); i <- i + 1
draw.plotmath.cell(expression(x^2), i, nr); i <- i + 1
draw.title.cell("Juxtaposition", i, nr); i <- i + 1
draw.plotmath.cell(expression(x * y), i, nr); i <- i + 1
draw.plotmath.cell(expression(paste(x, y, z)), i, nr); i <- i + 1
draw.title.cell("Lists", i, nr); i <- i + 1
draw.plotmath.cell(expression(list(x, y, z)), i, nr); i <- i + 1
# even columns up
i <- 20
draw.title.cell("Radicals", i, nr); i <- i + 1
draw.plotmath.cell(expression(sqrt(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(sqrt(x, y)), i, nr); i <- i + 1
draw.title.cell("Relations", i, nr); i <- i + 1
draw.plotmath.cell(expression(x == y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x != y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x < y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x <= y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x > y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x >= y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%~~\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%=~\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%==\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%prop\% y), i, nr); i <- i + 1
draw.title.cell("Typeface", i, nr); i <- i + 1
draw.plotmath.cell(expression(plain(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(italic(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(bold(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(bolditalic(x)), i, nr); i <- i + 1

# Need fewer, wider columns for ellipsis ...
nr <- 20
nc <- 2
make.table(nr, nc)
i <- 0
draw.title.cell("Ellipsis", i, nr); i <- i + 1
draw.plotmath.cell(expression(list(x[1], ..., x[n])), i, nr); i <- i + 1
draw.plotmath.cell(expression(x[1] + ... + x[n]), i, nr); i <- i + 1
draw.plotmath.cell(expression(list(x[1], cdots, x[n])), i, nr); i <- i + 1
draw.plotmath.cell(expression(x[1] + ldots + x[n]), i, nr); i <- i + 1
draw.title.cell("Set Relations", i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%subset\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%subseteq\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%supset\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%supseteq\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%notsubset\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%in\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%notin\% y), i, nr); i <- i + 1
draw.title.cell("Accents", i, nr); i <- i + 1
draw.plotmath.cell(expression(hat(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(tilde(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(ring(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(bar(xy)), i, nr); i <- i + 1
draw.plotmath.cell(expression(widehat(xy)), i, nr); i <- i + 1
draw.plotmath.cell(expression(widetilde(xy)), i, nr); i <- i + 1
draw.title.cell("Arrows", i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%<->\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%->\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%<-\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%up\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%down\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%<=>\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%=>\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%<=\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%dblup\% y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x \%dbldown\% y), i, nr); i <- i + 1
draw.title.cell("Symbolic Names", i, nr); i <- i + 1
draw.plotmath.cell(expression(Alpha - Omega), i, nr); i <- i + 1
draw.plotmath.cell(expression(alpha - omega), i, nr); i <- i + 1
draw.plotmath.cell(expression(infinity), i, nr); i <- i + 1
draw.plotmath.cell(expression(32 * degree), i, nr); i <- i + 1
draw.plotmath.cell(expression(60 * minute), i, nr); i <- i + 1
draw.plotmath.cell(expression(30 * second), i, nr); i <- i + 1

# Need even fewer, wider columns for typeface and style ...
nr <- 20
nc <- 1
make.table(nr, nc)
i <- 0
draw.title.cell("Style", i, nr); i <- i + 1
draw.plotmath.cell(expression(displaystyle(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(textstyle(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(scriptstyle(x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(scriptscriptstyle(x)), i, nr); i <- i + 1
draw.title.cell("Spacing", i, nr); i <- i + 1
draw.plotmath.cell(expression(x ~~ y), i, nr); i <- i + 1

# Need fewer, taller rows for fractions ...
# cheat a bit to save pages
par(new =T)
nr <- 10
nc <- 1
make.table(nr, nc)
i <- 4
draw.plotmath.cell(expression(x + phantom(0) + y), i, nr); i <- i + 1
draw.plotmath.cell(expression(x + over(1, phantom(0))), i, nr); i <- i + 1
draw.title.cell("Fractions", i, nr); i <- i + 1
draw.plotmath.cell(expression(frac(x, y)), i, nr); i <- i + 1
draw.plotmath.cell(expression(over(x, y)), i, nr); i <- i + 1
draw.plotmath.cell(expression(atop(x, y)), i, nr); i <- i + 1

# Need fewer, taller rows and fewer, wider columns for big operators ...
nr <- 10
nc <- 1
make.table(nr, nc)
i <- 0
draw.title.cell("Big Operators", i, nr); i <- i + 1
draw.plotmath.cell(expression(sum(x[i], i=1, n)), i, nr); i <- i + 1
draw.plotmath.cell(expression(prod(plain(P)(X == x), x)), i, nr); i <- i + 1
draw.plotmath.cell(expression(integral(f(x) * dx, a, b)), i, nr); i <- i + 1
draw.plotmath.cell(expression(union(A[i], i==1, n)), i, nr); i <- i + 1
draw.plotmath.cell(expression(intersect(A[i], i==1, n)), i, nr); i <- i + 1
draw.plotmath.cell(expression(lim(f(x), x \%->\% 0)), i, nr); i <- i + 1
draw.plotmath.cell(expression(min(g(x), x >= 0)), i, nr); i <- i + 1
draw.plotmath.cell(expression(inf(S)), i, nr); i <- i + 1
draw.plotmath.cell(expression(sup(S)), i, nr); i <- i + 1

make.table(nr, nc)
i <- 0
draw.title.cell("Grouping", i, nr); i <- i + 1
draw.plotmath.cell(expression((x + y)*z), i, nr); i <- i + 1
draw.plotmath.cell(expression(x^y + z), i, nr); i <- i + 1
draw.plotmath.cell(expression(x^(y + z)), i, nr); i <- i + 1
# have to do this one by hand
draw.plotmath.cell(expression(x^{y + z}), i, nr, string="x^{y + z}"); i <- i + 1
draw.plotmath.cell(expression(group("(", list(a, b), "]")), i, nr); i <- i + 1
draw.plotmath.cell(expression(bgroup("(", atop(x, y), ")")), i, nr); i <- i + 1
draw.plotmath.cell(expression(group(lceil, x, rceil)), i, nr); i <- i + 1
draw.plotmath.cell(expression(group(lfloor, x, rfloor)), i, nr); i <- i + 1
draw.plotmath.cell(expression(group("|", x, "|")), i, nr); i <- i + 1

par(oldpar)
}
\keyword{aplot}