Major math error with Grapher

Discussion in 'Mac Apps and Mac App Store' started by Papajohn56, Feb 7, 2008.

  1. Papajohn56 macrumors 6502

    Joined:
    Aug 13, 2005
    #1
    Using a factorial in Grapher results in an incorrect function output, it seems Grapher does the Gamma function rather than the standard step function for factorial. Take a look:

    [​IMG]

    Which gamma is actually defined as:
    [​IMG]

    rather than the true factorial:

    [​IMG]
     
  2. gauchogolfer macrumors 603

    gauchogolfer

    Joined:
    Jan 28, 2005
    Location:
    American Riviera
    #2
    How would you plot a factorial for negative numbers, anyways? Isn't that the whole point of the Gamma function, to account for real and complex numbers? Still, I'm not sure it counts as a 'Major Math Error'. Is there a different function indicator rather than ! that you could use for factorial?
     
  3. Papajohn56 thread starter macrumors 6502

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    Aug 13, 2005
    #3
    Exactly, that's the biggest problem, along with positive decimal factorials.
     
  4. gauchogolfer macrumors 603

    gauchogolfer

    Joined:
    Jan 28, 2005
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    American Riviera
    #5
    Thanks for the link, but I think we both know what the Gamma function is already. The OP would like to know why ! defaults to Gamma and not factorial, I imagine. Maybe it's because factorial is only defined for positive integers, and Grapher can only handle continuous functions? Iono.
     
  5. Papajohn56 thread starter macrumors 6502

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    Aug 13, 2005
    #6
    yeah, I know factorial and gamma are related, but they aren't the same. That's my concern
     
  6. MisterMe macrumors G4

    MisterMe

    Joined:
    Jul 17, 2002
    Location:
    USA
    #7
    The gamma function is defined over the range of negative non-integers, zero, and positive numbers. The factorial is not a step function. In the OP's parlance, the factorial function is defined only for zero and positive integral arguments. The OP cannot invoke non-integral arguments and then complain about the result.
     
  7. Papajohn56 thread starter macrumors 6502

    Joined:
    Aug 13, 2005
    #8
    Yes but Gamma and Factorial are not the same thing. As a matter of fact, for positive integers, Gamma is equal to (n-1)!, rather than just n!

    They are not the same function, even though they are related. When I enter factorial, I shouldn't get Gamma as the output.
     

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