# R-alpha: Mathematical Anotation in Plots

**Ross Ihaka
**
ihaka@stat.auckland.ac.nz

*Sun, 27 Jul 1997 16:19:47 +1200 (NZST)*

I forgot to mention that version 0.50 will do "greek" and "accents" in
plot labels. The basic idea is that you should be able to replace any
character vector by an expression vector when doing plot annotation.
E.g.
plot(rnorm(10),main=expression(hat(Theta)))
This produces a plot with a main title consisting of a capital Theta
with a "hat" on it. The idea is to use R parse trees to represent
mathematical expressions.
Most things are as you would expect, with the following exceptions:
o ^ is used for superscripting and [] for subscripting so that
x[i]^2 is the equivalent of the TeX x_i^2.
o you use over(x,y) for a fraction with x in the numerator and y
in the denominator.
o the *" operator is used to denote juxtaposition. sometimes this
makes sense - e.g. x*e^{x/lambda}, and sometimes it is a bit ugly
e.g. "Distribution of "*hat(Theta). I haven't thought of a
better solution (yet).
This is a very immature implementation, but you might enjoy playing
with it.
Ross
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