From help-octave-request at bevo dot che dot wisc dot edu Mon Sep 4 07:22:07 2000 Subject: Re: status lgamma V2.1.31 ? From: Paul Kienzle To: fabian at tu-cottbus dot de, help-octave@bevo.che.wisc.edu Date: Mon, 04 Sep 2000 13:22:21 +0100 From: Rolf Fabian >Hi, > >can anybody with access to an Octave V2.1.31 installation octave2.1:2> OCTAVE_VERSION OCTAVE_VERSION = 2.1.31 >give me some infos on status of built-in lgamma(x) >by testing the following simple commands > >:1> lgamma(-1/2) octave2.1:3> lgamma(-1/2) ans = 1.2655 > >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) octave2.1:4> lgamma(-2) ***MESSAGE FROM ROUTINE DGAMMA IN LIBRARY SLATEC. ***FATAL ERROR, PROG ABORTED, TRACEBACK REQUESTED * X IS A NEGATIVE INTEGER * ERROR NUMBER = 4 * ***END OF MESSAGE ***JOB ABORT DUE TO FATAL ERROR. 0 ERROR MESSAGE SUMMARY LIBRARY SUBROUTINE MESSAGE START NERR LEVEL COUNT SLATEC DGAMMA X IS A NEGATIVE INTE 4 2 4 error: exception encountered in Fortran subroutine dlgams >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) octave2.1:4> lgamma(1+i) error: lgamma: unable to handle complex arguments > >Thanks for any feedback >Rolf > > > > >----------------------------------------------------------------------- >Octave is freely available under the terms of the GNU GPL. > >Octave's home on the web: http://www.che.wisc.edu/octave/octave.html >How to fund new projects: http://www.che.wisc.edu/octave/funding.html >Subscription information: http://www.che.wisc.edu/octave/archive.html >----------------------------------------------------------------------- > > > ----------------------------------------------------------------------- Octave is freely available under the terms of the GNU GPL. Octave's home on the web: http://www.che.wisc.edu/octave/octave.html How to fund new projects: http://www.che.wisc.edu/octave/funding.html Subscription information: http://www.che.wisc.edu/octave/archive.html -----------------------------------------------------------------------