\Header{plotmath}{Mathematical Annotation in R}
\keyword{aplot}{plotmath}
\begin{Description}\relax
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.  Expressions can also be used for titles, subtitles and
x- and y-axis labels (but not for axis labels on \code{persp} plots).\end{Description}
\begin{Details}\relax
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.

The available features are also described in the tables below:

\Tabular{ll}{
\bold{Syntax} & \bold{Meaning} \\
\code{x + y}   & x plus y   \\
\code{x - y}   & x minus y \\
\code{x*y}    & juxtapose x and y \\
\code{x/y}    & x forwardslash y \\
\code{x \%+-\% y}   & x plus or minus y \\
\code{x \%/\% y}   & x divided by y \\
\code{x \%*\% y}   & x times y \\
\code{x[i]}   & x subscript i \\
\code{x\textasciicircum{}2}    & x superscript 2 \\
\code{paste(x, y, z)} & juxtapose x, y, and z \\
\code{sqrt(x)}   & square root of x \\
\code{sqrt(x, y)}   & yth root of x \\
\code{x == y}   & x equals y \\
\code{x != y}   & x is not equal to y \\
\code{x < y}   & x is less than y \\
\code{x <= y}   & x is less than or equal to y \\
\code{x > y}   & x is greater than y \\
\code{x >= y}   & x is greater than or equal to y \\
\code{x \%\textasciitilde{}\textasciitilde{}\% y}   & x is approximately equal to y \\
\code{x \%=\textasciitilde{}\% y}   & x and y are congruent \\
\code{x \%==\% y}   & x is defined as y \\
\code{x \%prop\% y}  & x is proportional to y \\
\code{plain(x)}   & draw x in normal font \\
\code{bold(x)}   & draw x in bold font \\
\code{italic(x)}   & draw x in italic font \\
\code{bolditalic(x)} & draw x in bolditalic font \\
\code{list(x, y, z)} & comma-separated list \\
\code{...}    & ellipsis (height varies) \\
\code{cdots}   & ellipsis (vertically centred) \\
\code{ldots}   & ellipsis (at baseline) \\
\code{x \%subset\% y} & x is a proper subset of y \\
\code{x \%subseteq\% y} & x is a subset of y \\
\code{x \%notsubset\% y} & x is not a subset of y \\
\code{x \%supset\% y} & x is a proper superset of y \\
\code{x \%supseteq\% y} & x is a superset of y \\
\code{x \%in\% y}   & x is an element of y \\
\code{x \%notin\% y} & x is not an element of y \\
\code{hat(x)}   & x with a circumflex \\
\code{tilde(x)}   & x with a tilde \\
\code{dot(x)} & x with a dot \\
\code{ring(x)}   & x with a ring \\
\code{bar(xy)}   & xy with bar \\
\code{widehat(xy)}   & xy with a wide circumflex \\
\code{widetilde(xy)} & xy with a wide tilde \\
\code{x \%<->\% y}   & x double-arrow y \\
\code{x \%->\% y}   & x right-arrow y \\
\code{x \%<-\% y}   & x left-arrow y \\
\code{x \%up\% y}   & x up-arrow y \\
\code{x \%down\% y}  & x down-arrow y \\
\code{x \%<=>\% y}   & x is equivalent to y \\
\code{x \%=>\% y}   & x implies y \\
\code{x \%<=\% y}   & y implies x \\
\code{x \%dblup\% y}   & x double-up-arrow y \\
\code{x \%dbldown\% y} & x double-down-arrow y \\
\code{alpha} -- \code{omega} & Greek symbols \\
\code{Alpha} -- \code{Omega} & uppercase Greek symbols \\
\code{infinity}   & infinity symbol \\
\code{partialdiff} & partial differential symbol \\
\code{32*degree}   & 32 degrees \\
\code{60*minute}   & 60 minutes of angle \\
\code{30*second}   & 30 seconds of angle \\
\code{displaystyle(x)} & draw x in normal size (extra spacing) \\
\code{textstyle(x)}  & draw x in normal size \\
\code{scriptstyle(x)} & draw x in small size \\
\code{scriptscriptstyle(x)} & draw x in very small size \\
\code{x \textasciitilde{}\textasciitilde{} y}        & put extra space between x and y \\
\code{x + phantom(0) + y} & leave gap for "0", but don't draw it \\
\code{x + over(1, phantom(0))} & leave vertical gap for "0" (don't draw) \\
\code{frac(x, y)}   & x over y \\
\code{over(x, y)}   & x over y \\
\code{atop(x, y)}   & x over y (no horizontal bar) \\
\code{sum(x[i], i==1, n)} & sum x[i] for i equals 1 to n \\
\code{prod(plain(P)(X==x), x)} & product of P(X=x) for all values of x \\
\code{integral(f(x)*dx, a, b)} & definite integral of f(x) wrt x \\
\code{union(A[i], i==1, n)} & union of A[i] for i equals 1 to n \\
\code{intersect(A[i], i==1, n)} & intersection of A[i] \\
\code{lim(f(x), x \%->\% 0)} & limit of f(x) as x tends to 0 \\
\code{min(g(x), x > 0)} & minimum of g(x) for x greater than 0 \\
\code{inf(S)}        & infimum of S \\
\code{sup(S)}   & supremum of S \\
\code{x\textasciicircum{}y + z}   & normal operator precedence \\
\code{x\textasciicircum{}(y + z)}    & visible grouping of operands \\
\code{x\textasciicircum{}\{y + z\}}  & invisible grouping of operands \\
\code{group("(",list(a, b),"]")} & specify left and right delimiters \\
\code{bgroup("(",atop(x,y),")")} & use scalable delimiters \\
\code{group(lceil, x, rceil)} & special delimiters \\
}\end{Details}
\begin{References}\relax
Murrell, P. and Ihaka, R. (2000) An approach to providing
mathematical annotation in plots.
\emph{Journal of Computational and Graphical Statistics},
\bold{9}, 582--599.\end{References}
\begin{SeeAlso}\relax
\code{\Link{axis}},
\code{\Link{mtext}},
\code{\Link{text}},
\code{\Link{title}}\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
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))

## How to combine "math" and numeric variables :
plot(1:10, type="n", xlab="", ylab="", main = "plot math & numbers")
tt <- 1.23 ; mtext(substitute(hat(theta) == that, list(that= tt)))
for(i in 2:9)
    text(i,i+1, substitute(list(xi,eta) == group("(",list(x,y),")"),
                           list(x=i, y=i+1)))

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=FALSE)
    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 = TRUE)
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)
\end{ExampleCode}
\end{Examples}

