Returns the derivative of the log gamma function, also
called the digamma function.
Namespace: Imsl.MathAssembly: ImslCS (in ImslCS.dll) Version: 6.5.2.0
Syntax public static double Psi(
double x
)
Public Shared Function Psi (
x As Double
) As Double
public:
static double Psi(
double x
)
static member Psi :
x : float -> float
Parameters
- x
- Type: SystemDouble
A double value, the point at which the
digamma function is to be evaluated.
Return Value
Type:
Double
A
double value specifying the logarithmic derivative of the
gamma function of
x. If
x is
a zero or a negative integer, the result is
NaN. If
x is too close to a negative integer the
accuracy of the result will be less than half precision.
Remarks The psi function is defined to be
See
Gamma for the definition of
.
The argument x must not be exactly zero or
a negative integer, or is undefined.
Also, x must not be too close to a negative
integer such that the accuracy of the result is less than half
precision.
See Also