text() in plot r code example
Example: how to add a text box in plot r
plot(1:10, 1:10,
main="text(...) examples\n~~~~~~~~~~~")
text(4, 9, expression(hat(beta) == (X^t * X)^{-1} * X^t * y))
text(7, 4, expression(bar(x) == sum(frac(x[i], n), i==1, n)))