[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## norm( x ) = inf for x > sqrt( realmax )

**From**: |
Andy Adler |

**Subject**: |
norm( x ) = inf for x > sqrt( realmax ) |

**Date**: |
Sun, 30 Oct 2005 05:32:49 -0500 (EST) |

I'd like to point of a difference between octave
and the competition.
for any x > sqrt( realmax )
octave (cvs build) gives norm( x) = inf,
while Matlab (>=6.5) gives the correct value
(I just checked an old octave (2.1.42) and got
octave:1> norm(1.35e154)
ans = NaN + NaNi )
There seems to be some special logic in the Matlab
norm function, because making the calculation by hand
gives inf
>*> P=2;V= realmax; sum(abs(V).^P)^(1/P)*
ans =
Inf
>*> norm(V)*
ans =
1.7977e+308
--
Andy Adler <address@hidden> 1(613)562-5800x6218

**norm( x ) = inf for x > sqrt( realmax )**,
*Andy Adler* **<=**