Prof Brian Ripley
ripley at stats.ox.ac.uk
Wed Mar 29 10:00:23 CEST 2006
On Wed, 29 Mar 2006, Robin Hankin wrote:
> Hi guys
> perhaps my original message wasn't so clear.
> My point was that the documentation is inconsistent with the
I think it is _your reading_ of the documentation that is inconsistent.
An equally plausible reading is that both x and y must be numeric or
> How to remedy this?
> (i) add a line to Trig.Rd along the lines of "atan2() will not work
> if the first argument
> is real and the second argument complex"
> (ii) Modify atan2() so that it coerces the first argument to a
> complex if necessary.
> I'd prefer option (ii) but can't see a quick fix.
Really? It's a one-line change.
BTW, this *really* is an R-devel topic, so please try to use the
appropriate list. Suggestions for changes to R get lost in the torrent of
R-help extremely easily.
And only the designers can say
'but atan2 wasn't originally designed for complex arguments.'
but the code suggests otherwise.
> On 28 Mar 2006, at 19:52, Jeff Newmiller wrote:
>> Robin Hankin wrote:
>>> ?atan2 says that atan2(y,x)=atan(y/x) for x and y numeric or complex
>>> Well, I would expect atan2(1,1i) to be equal to atan(-1i), but
>>> Error in atan2(y, x) : Non-numeric argument to mathematical function
>> Ravi Varadhan pointed out that you need to make both arguments complex
>> to address the error message you obtained... but atan2 wasn't
>> designed for complex arguments. I suspect that what you really want is
>> to use the Arg function:
>>  -1.570796
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
> tel 023-8059-7743
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Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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