Re: Newbie - can't find function

[Paul Kienzle]

On Sat, Apr 21, 2001 at 01:55:30PM +0100, Matteo Bettella wrote:
> 
> On Sat, 21 Apr 2001, Brent W. Woodruff wrote:
> 
> > Hello,
> > I'm new to the world of octave and despite my best efforts in the function 
> > index and help files, I can't find the command for mod.  Is it in there or 
> > do 
> > I need to write an octave program to do it?
> > 
> 
> I think you don't.
> >From the documentation:
> 
> Mapping Function: rem (x, y) 
> Return the remainder of x / y, computed using the expression 
> 
> x - y .* fix (x ./ y)
> 
> An error message is printed if the dimensions of the arguments do not
> agree, or if either of the arguments is complex. 
> 
> 
> Is this what you need?
> Regards,
> Matteo
> 

This won't work corrrectly for negative valued x.  Instead you want

        x - y .* floor (x ./ y)

Another caveat is that Matlab's function mod(x,0) returns x, so for
complete compatibility you must trap for y == 0.  Although arguably
wrong since lim_{y -> 0}{x-y*floor(x/y)} = 0, this behaviour is
implemented in:

http://users.powernet.co.uk/kienzle/octave/matcompat/scripts/specfun/mod.m

Paul Kienzle
address@hidden

> 
> 
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