[R] Drawing a colour wheel - bug in hcl?
Achim.Zeileis at wu-wien.ac.at
Tue Jul 8 00:12:50 CEST 2008
On Mon, 7 Jul 2008, hadley wickham wrote:
>> If you replace this by
>> hcl$colour <- hcl(hcl$h, hcl$c, hcl$l, fixup = FALSE)
>>> with(hcl, plot(x, y, col=colour, pch=20))
>> Then, the resulting "wheel" has three overlapping "holes" corresponding to
>> the colors previously fixed.
> Oops, thanks for pointing that out.
>> Also, as hue/chroma correspond to polar coordinates in the UV plane of
>> CIELUV, it makes more sense to plot wheels in the hue/chroma plane for fixed
>> luminance. To draw a hue/luminance plane for fixed chroma is harder to
>> interpret geometrically.
> Oooh, I guess if I'd thought about that for a couple of seconds I
> would have a realised that! What are good values to use for luminance
> and chroma in that case?
There are some utility visualization functions in the devel-version of
"colorspace" on R-Forge. Try:
> I can't seem to find a slice which gives me
> a decently wheel-like slice? Or should I just use fixup = TRUE, or
> accept that true colour wheels displayed on rgb monitors don't look
> like wheels?
They always look a bit awkward, more like rectangles or triangles, but you
could limit the maximum chroma, then it looks a bit more like a wheel.
hue_chroma_plane(c = 0:50)
But you can never get the full wheel if you want to balance with respect
to luminance. Or conversely, if you construct a wheel like
then it is not balanced with respect to lumincance.
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