psi( [ n , ] z )

The digamma function of z in SageMath. Defined by

The optional integer argument n is used for multiple derivatives.

Plot on the real axis:

show( plot( psi(x), x, -5, 5, figsize=[4.5,2], color=(0,.5,1),

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Series expansion about the origin:

show( maxima( psi(z) ).taylor(z,0,3) )

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Special values:

show( psi(0,hold=True), '=', -oo ) # psi(0) )

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Related functions:   gamma

Function category: gamma functions sagemath-docs