Zoo panel function

Achim,

Thank you for your response, and for your work on the zoo package in
general.  Also, that implementation of the color scheme looks great.

Frankly, I can't remember exactly what I was originally trying to
accomplish for this particular problem, but I think that your suggestion of
reviewing the plotting section of the zoo vignette would solve the problem.
 Calculating the colors ahead of time and passing them in as a list is
great solution that I didn't know was possible.

I still have some lingering questions about the panel function, which has
been one of those things in R that I would like to understand better.

Using your example, I would like to be able to pass in an additional
variable to make each set of hues like this:

mycol <- function(i, v)  hcl(
  h = ifelse(i > 0, v, 0),
  c = 80 * abs(i)^1.5,
  l = 90 - 60 * abs(i)^1.5)

mypanel <- function(x, y, v, ...) {
  lines(x, y, col = "gray")
  points(x, y, col = mycol(y / max(abs(y)), v), pch = 19)
}
plot(zobj, panel = mypanel, v=0)
plot(zobj, panel = mypanel, v=50)
plot(zobj, panel = mypanel, v=100)
plot(zobj, panel = mypanel, v=150)


This runs, but generates warnings. I was trying to find the right way to
pass additional arguments to panel.

I was trying things like this:
plot(zobj, panel = mypanel(x, y, v=150))
plot(zobj, panel = mypanel(..., v=150))


I was surprised at how many ways I could call panel, but how unpredictable
(to me) the results were!  Things that I didn't think would work were ok,
and other things that seemed correct would threw errors.

If you have some insight I would like to hear it, but this isn't that
important because there are obviously other approaches for making the same
/ similar output.