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How to simplify certain covariance expressions using

  • To: mathgroup at smc.vnet.net
  • Subject: [mg128027] How to simplify certain covariance expressions using
  • From: hewei2004 at gmail.com
  • Date: Sun, 9 Sep 2012 17:33:24 -0400 (EDT)
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  • Delivered-to: l-mathgroup@wolfram.com
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Hi,

  I have a certain case of covariance to simplify. 

Suppose I have the following expression:
cov=(ea+ex)(ea+ey)=eaea+eaex+eaey+exey

How can I assume that whenever ex times ey ,the product is 0, so that the expression I want to get out of is

Assuming[exey=0,Refine[cov]]=eaea+eaex+eaey
So that the last term:exey, drops out. 

My problem is that the Assuming[] function won't take exey=0 as a valid assumption. Is there any way to do this using some other function or I typed something wrong?



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