First a bit of background:
After doing a search for a flexible polar plot function and coming up empty, I have begun writing one myself. Since I am new to writing mid-level graphics routines, this has required some learning about lattice, grid and related things.
I am to the point where I have a workable proof of concept, but still need to make some improvements. My goal is to have something akin to a polar version of xYplot. Although the particular plot I need requires some customization of that idea, the use of Cbind() has made that fairly easy.
Now some questions:
1) What are the best sources of documentation for lattice/grid? I have found a few things by googling, but mostly I have been reverse engineering code and experimenting to figure out how things work.
2) What is the best way to generate "axis" and labels for them?
Currently my radplot is a wrapper for xyplot that (a) turns off the axes and labels, and (b) calls xyplot with panel.radplot, prepanel.radplot, and radplot.superpose replacing the obvious things. I am generating the "axes" (concentric circles and peripheral labels) in panel.radplot, but this means that they are redrawn for each group when there is superposition. Furthermore, there seems to be some jittering, so besides inefficiency, the result is not crisp.
How are axes generated in xyplot? To do this correctly will I have to go deeper and make a new version of trellis.skeleton or make a new call to it? If I put the code into prepanel.radplot will it be executed once per panel or once per group in each panel?
3) I'd be happy to receive any other suggestions for how to approach the design of a robust, formula-based (including xYplot-like options) radial/polar plot. I'd also be happy to hear of any packages that include something heading in this direction, if they exist and I just didn't locate them.
Thanks in advance for any assistance.
---rjp
PS. For the curioius, the plot I am designing has a function call like
radplot(Cbind(y,ratio)~x|g, groups=h, ...)
where y is numeric and x may be numeric or a factor. The resulting plot has "spokes" for each value of x with length y, the last 1 - min(ratio, 1/ratio) fraction of the spoke rendered differently. This is similar to adding error bars to a plot in xYplot -- only in polar coordinates.
============================================== Randall Pruim Dept. of Biostatistics, University of Michigan
email: [EMAIL PROTECTED] phone: 734.615.9825
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