panel.qqmathline: Useful panel function with qqmath
Description
Useful panel function with qqmath. Draws a line passing through the
points (usually) determined by the .25 and .75 quantiles of the sample
and the theoretical distribution.
Usage
panel.qqmathline(x, y = x,
distribution = qnorm,
p = c(0.25, 0.75),
qtype = 7,
groups = NULL,
...)