[R] Drawing a colour wheel - bug in hcl?

hadley wickham h.wickham at gmail.com
Mon Jul 7 21:47:05 CEST 2008

On Mon, Jul 7, 2008 at 1:05 PM, Earl F. Glynn <efg at stowers-institute.org> wrote:
> "hadley wickham" <h.wickham at gmail.com> wrote in message
> news:f8e6ff050807070906y272bf4b9u7a356a5da0850653 at mail.gmail.com...
>>  there's some
>> oddly bright colours of the wrong hue around c(0, 0) and I see three
>> coloured circles (a small magenta, a medium sized yellow and a large
>> cyan).  Am I doing something wrong or is there a bug in the hcl code?
> You set c = 70 = constant
> from ?hcl:
>      c  The chroma of the color. The upper bound for chroma depends on hue
> and luminance
> You seem to have used the full range of possible hue and luminance values.
> Perhaps your odd colored circles are violations on valid values of chroma?

Well, I do have fixup = FALSE, which the documentation indicates
should return NA if the chroma exceeds the actual upper bound.

> Also, using "hcl" in different ways in the same code is also discouraged by
> "Code Complete 2".  Again on p. 287:  "Avoid the names of standard types,
> variables, and routines."   If "hcl" is a "standard" routine, using "hcl" as
> a variable name in the same code example using the "hcl" function is not
> recommended and is confusing.

Yes, that's true!



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