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ptc-48710361-Visitor
1-Visitor
December 9, 2012
Question

Polygamma function in cycle

  • December 9, 2012
  • 2 replies
  • 3335 views

Good day,

I have a problem with the psi(1,y) function.

y_i are the Maxwell random variables, which I generate.

Program is attached.

I would be happy for your answers.

2 replies

S
StuartBruff23-Emerald V
23-Emerald V
December 9, 2012

The Psi function only takes one parameter; try just Psi(y).

Stuart

V
24-Ruby III
VladimirN24-Ruby III
24-Ruby III
December 9, 2012

Stuart,

The digamma function, Psi(x), is defined to be the derivative of the natural logarithm of the Gamma function Γ(x).

The polygamma function, Psi(k, x), is defined to be the kth derivative of the Gamma function.

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StuartBruff23-Emerald V
23-Emerald V
December 13, 2012

That will teach me to read the documentation instead of just looking at the error message (... well, it won't. Unfortunately, I have never been possessed of 100 % hindsight and am perfectly capable of replicating the same error )

Stuart

R
RichardJ19-Tanzanite
19-Tanzanite
December 9, 2012

Mathcad has two processors: one for symbolic math, and one for numeric math. The Psi function is only defined for symbolic math. That's easily remedied though.

    P
    ptc-48710361-VisitorAuthor
    1-Visitor
    December 9, 2012

    U saved me!

    That was really easy, this was my first idea but without vectorization...and it didn't work...

    Thx a lot one more time

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