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Re: fractional remainder

From: David Bateman
Subject: Re: fractional remainder
Date: Mon, 26 Dec 2005 09:57:04 +0100
User-agent: Mozilla Thunderbird 0.8 (X11/20040923)

kamaraju kusumanchi wrote:

blah BLABBER wrote:

Howdy folks,

Question: I am a new Octave user and cannot figure out how to grab the remainder of a fraction. For example, if I take 3/4 = 0.75, I just want to grab the 75.

Reason: I would like to check if the remainder is zero in order to determine if a number is odd or even. Any even number divided by 2 will have a remainder of 0, odd numbers will not. I am using this for loop control.

Problem: In Octave, rem(3,4) gives 3. Obviously I do not understand this function. Can you please suggest the appropriate function to use.


Try the mod function.

octave:1> mod(11,2)
ans = 1
octave:2> mod(10,2)
ans = 0
octave:3> mod(3,4)
ans = 3
octave:4> mod(7,4)
ans = 3

To read about a function you can use the help command. To read about rem, type help rem at the octave prompt etc.,


If your goal is to see if an integer is odd/even try the bitand function. In C the typical way to check if an integer is odd if

if (val & 1)
   /* This value is odd */
   /* This value is even */

The equivalent in octave would be

if (bitand (val, 1))
  # This value is odd
  # This value is even

This should probably be faster than mod.


David Bateman                                address@hidden
Motorola Labs - Paris +33 1 69 35 48 04 (Ph) Parc Les Algorithmes, Commune de St Aubin +33 1 69 35 77 01 (Fax) 91193 Gif-Sur-Yvette FRANCE

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