Re: Zero times a variable in numerical calculations
- To: mathgroup at smc.vnet.net
- Subject: [mg68365] Re: Zero times a variable in numerical calculations
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Thu, 3 Aug 2006 06:06:22 -0400 (EDT)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
Use Rationalize 0.0 * a // Rationalize 0 Bob Hanlon ---- Maurits Haverkort <Haverkort at ph2.uni-koeln.de> wrote: > Dear All > > > > I have the following problem. > > In: 0.0 a > > Out 0. a > > > > I would like to have that > > In: 0.0 a > > Simplifies to > > Out: 0 > > > > SetPrecision[0.0 a,10^-100] works, but I am a bit puzzled > > > > 0.0 ==0 returns true > > 0.0 a == 0 a returns unevaluated to 0.0 a == 0 > > > > This seems inconsistent to me. > > > > 1) Could anyone explain me the logic behind this? > > 2) What is the fastest way to multiply a numerical matrix times a half numerical half analytical sparse matrix, whereby the result is band diagonal. (The current result has 0. a + 0. b + 0. c + 0. d + 0. e + 0. f on all places where it should be zero.) > > > > Thanks in advance. > > Maurits Haverkort