>>>>> "TS" == Timur Shtatland <[EMAIL PROTECTED]>
>>>>> on Fri, 12 Sep 2008 11:52:25 -0400 writes:
TS> I am more used to getting an error if you try to take
TS> the log of 0, like this (in Perl):
TS> perl -le 'for my $num (1, 0, -1, -2) { print log $num;
TS> }' 0 Can't take log of 0 at -e line 1.
TS> R is different. With R, you do not even get a *warning*
TS> about log(0). Only log() of negative number produces a
TS> warning:
[............]
and why do you think the perl behavior to be better??
R has been very carefully designed in such matters:
The principle is that *limits* should work (using +/-Inf) were
possible.
For log(.) the limit only exists from the right and clearly is
-Inf, so that's a feature.
BTW, S/R behavior of 1/0 |--> Inf could be considered as
more dangerous, since really the +Inf is the limit from the
right only with the limit from the left being ``quite
different''.
But no, I'm not proposing to change R here (and actually would
"fight" to keep it if that was necessary).
TS> I agree with you that Spearman's correlation's invariance to monotone
TS> transformations is an advantage. It is R's happy
TS> attitude to -Inf and Inf that puzzled me at
TS> first. Anyhow, verifying and/or preprocessing the input
TS> to cor() is the answer to my questions. Thank you again
TS> for the help!
So you now have understood that R's behavior of handling +/- Inf
in this respect is rather excellent than bogous ?
Martin Maechler, ETH Zurich (and R-core team)
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