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## status lgamma V2.1.31 ?

**From**: |
Rolf Fabian |

**Subject**: |
status lgamma V2.1.31 ? |

**Date**: |
Mon, 4 Sep 2000 09:49:44 +0200 |

Hi,
can anybody with access to an Octave V2.1.31 installation
give me some infos on status of built-in lgamma(x)
by testing the following simple commands
:1> lgamma(-1/2)
My current installations V2.0.13 cygwin32
(win95 precompiled) and V2.1.14 (OS/2) both fail
:1>lgamma(-1/2) |- 1.2655 << FALSE
because a non-zero imaginary part -+pi*i is expected,
which seems to be rejected silently from the result.
In case that an imag part is now correctly returned
by V2.1.31, what's it's sign?
Both -pi*i and +pi*i are actually possible, because
the complex logarithm function is periodical with a
period of 2*pi*i, so that the sign depends on some
(more or less arbitrary) definition.
Furthermore, what's the result for the poles on the
negative real axis?
:2> lgamma(-1)
:3> lgamma(-2)
Is is always Inf or do any imag parts occur?
Finally, does V2.1.31 allow for complex arguments now?
:4> lgamma( 1+i)
:5> lgamma(-1+i)
Thanks for any feedback
Rolf
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**status lgamma V2.1.31 ?**,
*Rolf Fabian* **<=**