Re: cm.colors bug (PR#244)

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Subject: Re: cm.colors bug (PR#244)
From: Martin Maechler (maechler@stat.math.ethz.ch)
Date: Tue 10 Aug 1999 - 02:29:55 EST


Message-Id: <199908091629.SAA11554@sophie.ethz.ch>

david> Full_Name: David M. Potter Version: 0.64.1 OS: solaris 2.6
david> Submission from: (NULL) (12.18.36.220)

david> cm.colors() returns an extra element "1":

Yes, this is a bug
    ....

david> Why I think it happens

david> The function has an unnecessary right parentheses immediately
david> preceding ", v=1" which causes the "v=1" to be added to the
david> vector rather than being interpreted as an argument to hsv().

david> > cm.colors
david> function (n)
david> {
david> k <- n%/%2
david> if (2 * k == n) {
david> c(hsv(h = 6/12, s = seq(0.5, 0, length = k + 1)[-k -
david> 1], v = 1), hsv(h = 10/12, s = seq(0, 0.5, length = n -
david> k + 1)[-1]), v = 1)
david> }
david> else {
david> c(hsv(h = 6/12, s = seq(0.5, 0, length = k + 1), v = 1),
david> hsv(h = 10/12, s = seq(0, 0.5, length = n - k)[-1]),
david> v = 1)
david> }
david> }

Correct.
There were more problems :
cm.colors(1) {and cm.colors(0)} both failed as well.

The following seems to be correct in all cases

cm.colors <- function (n)
{
    if ((n <- as.integer(n[1])) > 0) {
        even.n <- n %% 2 == 0
        k <- n%/%2
        l1 <- k + 1 - even.n
        l2 <- n - k + even.n
        c(if(l1 > 0)
          hsv(h = 6/12, s= seq(.5, ifelse(even.n,.5/k,0), length = l1), v = 1),
          if(l2 > 1)
          hsv(h = 10/12, s= seq(0, 0.5, length = l2)[-1], v = 1))
    } else character(0)
}

I'll commit it for the R-devel [daily snapshot] and hence 0.65.

Martin Maechler <maechler@stat.math.ethz.ch> http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum SOL G1 Sonneggstr.33
ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND
phone: x-41-1-632-3408 fax: ...-1086 <><
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