Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Interchanging discrete summation signs

  1. Apr 21, 2008 #1

    tgt

    User Avatar

    When needed to do that, I found it much easier to pretend it's an integral summation and then draw the area diagram then work it out from the picture the new terminals for the integral. Then convert that back into the discrete sum. Is that how you would do it?

    However for three or more variables that method could be tough. How would you do it then? Both for discrete and continous cases.
     
  2. jcsd
  3. Apr 21, 2008 #2

    quasar987

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Are we talking about an infinite sum or a finite sum?

    For the infinite case, Fubini's theorem for the Lebesgue integral applied to the counting measure gives conditions for when interchanging summation sign is legal.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Interchanging discrete summation signs
  1. Summation question (Replies: 3)

  2. Summation Verification (Replies: 6)

Loading...