On Mon, 16 May 2005, Robin Hankin wrote:
Hi
the following gave me a shock:
atan(2)
[1] 1.107149
atan(2+0i)
[1] -0.4636476+0i
or, perhaps more of a gotcha:
atan(1.0001+0i)
[1] -0.7853482+0i
atan(0.9999+0i)
[1] 0.7853482+0i
evidently atan()'s branch cuts aren't where I thought they were.
Where do I look for documentation on this?
In the sources. Specifically for complex atan() in src/main/complex.c
/* Complex Arctangent Function */
/* Equation (4.4.39) Abramowitz and Stegun */
static void z_atan(Rcomplex *r, Rcomplex *z)
...
--
Brian D. Ripley, [EMAIL PROTECTED]
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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