digamma function


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digamma function

[′dī‚gam·ə ‚fəŋk·shən]
(mathematics)
The derivative of the natural logarithm of the gamma function.
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Merkle, Convexity, Schur-convexity and bounds for the gamma function involving the digamma function, Rocky Mountain J.
as well, where [PSI](n, x) is the nth polygamma function, which is the nth derivative of the digamma function, [PSI](x) := (ln([GAMMA](x)))'= [GAMMA]'(x)/[GAMMA](x).
is the Eider's constant), which is known in literature as psi or digamma function.
The psi or digamma function [psi](x) = [GAMMA]'(x)/[GAMMA](x), the logarithmic derivative of the gamma function, and the polygamma functions can be expressed for x > 0 and k = 1, 2, .
The psi or digamma function, the logarithmic derivative of the gamma function and the polygamma functions can be expressed as