Re: Zero times a variable in numerical calculations
- To: mathgroup at smc.vnet.net
- Subject: [mg68396] Re: Zero times a variable in numerical calculations
- From: "Chris Chiasson" <chris at chiasson.name>
- Date: Thu, 3 Aug 2006 06:07:29 -0400 (EDT)
- References: <A56895C7CA4FC73.5FEF25D660@comcast.net> <001a01c6b610$89380640$69425f86@haverkort>
- Sender: owner-wri-mathgroup at wolfram.com
I guess this happens because you are using inexact numbers. Try using exact numbers or use Chop. On 8/2/06, 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 -- http://chris.chiasson.name/