R. SIMBOLI (altri usi)
If the text argument to one of the text-drawing functions (text, mtext, axis, legend) in R is an expression, the argument is interpreted as a mathematical expression and the output will be formatted (according to Teχ-like rules).
Expressions can also be used for titles, subtitles and x- and y-axis labels (but not for axis labels on persp plots).
It is possible to produce many different mathematical symbols, generate sub- or superscripts, produce fractions, etc.
The output from demo(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.

# Esempio:
plot(c(0,1),c(0,1),type="n",xlab="", ylab="")
text(0.25,3/4,expression(2*pi))
text(0.75,3/4,expression(a%.%b))
text(1/2,1/4,expression(bar(x) == sum(frac(x[i],n), i==1,n)))
text(1/2,0.5,expression(k^m))

# Altro esempio, in cui si mescolano uscite numeriche [vedi l'uso di
# .( ) e di bquote: del termine racchiuso in .() è valutato il valore
# (con expression o quote ne sarebbe scritta solo l'espressione]
plot(c(0,1),c(0,1),type="n",xlab="", ylab="")
for (i in 1:9) {v <- 1/10*i; text(1/2,v,bquote(sqrt(x,3) == .(v)),col="red")}

# Elenco dei comandi in  demo(plotmath)