The Digamma Function
Usage
digamma(z)
Arguments
z
Vector argument. May be real or complex but must have positive real part.
Description
Calculates the digamma function, which is the first derivative of the logarithm of the gamma function, for complex vector arguments.
Details
Uses an asymptotic expansion where Re(z) > 5 and a recurrence formula to such a case where Re(z) <= 5. Accuracy is good.
Value
Vector of digamma(z) values.
References
M. Abramowitz and I. A. Stegun (1965)
Handbook of Mathematical Functions.
Dover.
See Also
trigamma
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