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MathGroup Archive 1998

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Re: Getting rid of annoying zeroes in algebraic expressions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15236] Re: Getting rid of annoying zeroes in algebraic expressions
  • From: Harald Giese <giese at dkrz.de>
  • Date: Sun, 27 Dec 1998 03:58:29 -0500
  • Organization: Institut fuer Meereskunde, Universitaet Hamburg
  • References: <75q1n1$23s@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

"Ross, Sean" wrote:
> 
> Let xx be the result of some algebraic manipulations which, for some
> reason, mathematica thinks the real zeroes ought to be kept and I think
> they ought to be dropped.
> 
> xx=0. + (a*f)/(0. + f) + (b*f)/(0. + f) + (c*f)/(0. + f)
> 
> xx/.Plus[0.,q_]->q
> 
> returns
> 
> 0. + (a*f)/(0. + f) + (b*f)/(0. + f) + (c*f)/(0. + f)
> 
> while
> 
> 0. + (a*f)/(0. + f) + (b*f)/(0. + f) + (c*f)/(0. + f)/.Plus[0.,q_->q]
> 
> returns the expected
> 
> a+b+c.
> ...

Hi,


Mathematica keeps the approximate zeros "0.", because it regards the
symbols a, ..., f as expressions with indefinite precision. (See the
Mathematica book: Section 3.1.4. for that topic.)

Try

xx /. {0. -> 0}

or

Chop[xx]


-- 
Harald Giese
Email: giese at dkrz.de
Phone: +49 (0)40 4123 5796; Fax: +49 (0)40 5605724 Institut fuer
Meereskunde der Universitaet Hamburg (Institute of Oceanography of the
University of Hamburg) Troplowitzstrasse 7, D-22529 Hamburg


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