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Math object that returns 0 at k=0, 1 at k>0?

  1. Oct 13, 2012 #1
    Hello,

    I'm using summation notation (from k=0 to n) and would like a mathematical object to:

    return 0 when k=0
    return 1 when k>0

    I messed around with binomial coefficients but couldn't make it work. It's probably trivial, but I couldn't find it after much googling.
     
    Last edited: Oct 13, 2012
  2. jcsd
  3. Oct 13, 2012 #2

    haruspex

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    You could use a Green's function, or a Kronecker delta, but these are nonstandard functions. No smooth function will do what you want. Why do you need it?
     
  4. Oct 13, 2012 #3
    Definitely don't need anything smooth. I am trying to write out integration by parts to the nth derivative of the function g, and I am trying to sum up the boundary terms that pop out of higher n's. I want to be general enough to allow for n=0, which would mean there is no boundary terms and would need the sum to be killed off. Is there a simpler way to do it than:

    kroenecker_delta(0,kroenecker_delta(k,0))
     
  5. Oct 13, 2012 #4

    haruspex

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    I was thinking of 1-kroenecker_delta(k,0)
     
  6. Oct 14, 2012 #5

    Filip Larsen

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