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## apparently wrong description of 'arg' function in octave-3.0.5

**From**: |
Sergei Steshenko |

**Subject**: |
apparently wrong description of 'arg' function in octave-3.0.5 |

**Date**: |
Sun, 17 Apr 2011 05:55:35 -0700 (PDT) |

Hello,
in octave-3.0.5 'help arg' produces:
"
-- Mapping Function: arg (Z)
-- Mapping Function: angle (Z)
Compute the argument of Z, defined as THETA = `atan (Y/X)'. in
radians.
".
According to Wiki and my memories from school:
http://en.wikipedia.org/wiki/Inverse_trigonometric_functions :
arctangent y = arctan x x = tan y all real numbers −π/2 <
y < π/2 −90° < y < 90°
, i.e. the ranges equivalently are:
−π/2 < y < π/2 −90° < y < 90°
.
The above ranges are insufficient for complex numbers - the range in
radians should be either
-pi .. pi
or
0 .. 2 * pi.
In reality the 'arg' function works correctly:
"
octave:23> 180 / pi * arg(-1 + 0.01i)
ans = 179.43
octave:24> 180 / pi * arg(-1 - 0.01i)
ans = -179.43
",
i.e. it implements -pi .. pi (-180 .. 180 degrees) range - opposed to
what its built-in help message says (because of 'atan' and it's
-pi/2 .. pi/2 range).
Is the description fixed in later 'octave' versions ?
If not, should I file a bug report or this message is sufficient ?
...
'arg' behaves in accordance with 'man 3 carg' which is OK.
Thanks,
Sergei.

**apparently wrong description of 'arg' function in octave-3.0.5**,
*Sergei Steshenko* **<=**