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MathGroup Archive 2005

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Eliminating Annoying Minus Signs

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58756] Eliminating Annoying Minus Signs
  • From: "David Park" <djmp at earthlink.net>
  • Date: Sun, 17 Jul 2005 03:04:06 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Here is an expression that has annoying minus signs in it.

test = {-((2*x)/(-1 + z)), -((2*y)/(-1 + z)), -1}; 

We can get rid of them with the following operation.

MapAt[Minus, test, {{1, 1}, {1, 3, 1}, {2, 1}, {2, 3, 1}}]
{(2*x)/(1 - z), (2*y)/(1 - z), -1}

But it involves ferreting out the two positions at which we want to change signs and so is a little tedious and error prone.

Does someone have a simpler method for simplifying such expressions, which occur quite often with Mathematica?

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/ 


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