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Re: Collecting Positive and Negative Terms

• To: mathgroup at smc.vnet.net
• Subject: [mg112320] Re: Collecting Positive and Negative Terms
• From: Ray Koopman <koopman at sfu.ca>
• Date: Thu, 9 Sep 2010 04:22:57 -0400 (EDT)
• References: <i45rc9$g2p$1@smc.vnet.net> <i67583$8a8$1@smc.vnet.net>

On Sep 7, 9:59 pm, Michael Knudsen <micknud... at gmail.com> wrote:
> On Aug 14, 12:32 pm, Bob Hanlon <hanl... at cox.net> wrote:
>
>> myExpression = a + b - c;
>>
>> DeleteCases[myExpression, Times[-1, ___]]
>>
>> a+b
>
> Dammit! I was a little too fast with my reply. For some reason, it
> fails when I apply to one of my big expressions. Both postive and
> negative terms survive then.
>
> Here is an example of when it goes wrong:
>
> http://commondatastorage.googleapis.com/michael_knudsen_various/SplitExpression.nb
>
> --
> Michael Knudsen

Try   Cases[myExpression,Times[_?Negative,__]]  and
DeleteCases[myExpression,Times[_?Negative,__]] .