[R] OSX-specific Bug in randomForest

[Martin Maechler]

>>>>> Duncan Murdoch 
>>>>>     on Wed, 23 Oct 2024 05:33:57 -0400 writes:

    > I've cc'd this to the package maintainer, Andy Liaw
    > <andy_liaw using merck.com>. I'm not sure he reads this list.

    > Duncan Murdoch

Also, note that you should check for absolute difference, i.e.,

   if (abs(sum(cutoff) - 1) > .Machine$double.eps || ...

and I'd really recommend

   if (isTRUE(all.equal(1, sum(cutoff)))  || ....

Martin Maechler


    > On 2024-10-23 1:26 a.m., Stevie Pederson wrote:
    >> Hi,
    >> 
    >> It appears there is an OSX-specific bug in the function
    >> `randomForest.default()` Going by the source code at
    >> https://github.com/cran/randomForest/blob/master/R/randomForest.default.R
    >> the bug is on line 103
    >> 
    >> If the vector `cutoff` is formed using `cutoff <-
    >> rep(1/9, 9)` (line #101) the test on line 103 will fail
    >> on OSX as the sum is greater than 1 due to machine
    >> precision errors.
    >> 
    >> sum(rep(1 / 9, 9)) - 1 # [1] 2.220446e-16
    >> 
    >> This will actually occur for a scenario when the number
    >> of factor levels (nclass) is 9, 11, 18, 20 etc.The
    >> problem does not occur on Linux, and I haven't tested on
    >> WIndows.
    >> 
    >> A suggestion may be to change the opening test
    >> 
    >> if (sum(cutoff) > 1 || ...)
    >> 
    >> to
    >> 
    >> if (sum(cutoff) - 1 > .Machine$double.eps || ...
    >> 
    >> however, I'm sure there's a more elegant way to do this
    >> 
    >> Thanks in advance
    >> 
    >> [[alternative HTML version deleted]]
    >> 
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    > ______________________________________________
    > R-help using r-project.org mailing list -- To UNSUBSCRIBE and
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    > PLEASE do read the posting guide
    > https://www.R-project.org/posting-guide.html and provide
    > commented, minimal, self-contained, reproducible code.