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Function std.mathspecial.betaIncomplete
Incomplete beta integral
real betaIncomplete
(
real a,
real b,
real x
) pure nothrow @nogc @safe;
Returns incomplete beta integral of the arguments, evaluated from zero to x. The regularized incomplete beta function is defined as
betaIncomplete(a, b, x) = Γ(a + b) / ( Γ(a) Γ(b) ) * ∫0x ta-1(1-t)b-1 dt
and is the same as the the cumulative distribution function.
The domain of definition is 0 <= x <= 1. In this implementation a and b are restricted to positive values. The integral from x to 1 may be obtained by the symmetry relation
betaIncompleteCompl(a, b, x ) = betaIncomplete( b, a, 1-x )
The integral is evaluated by a continued fraction expansion or, when b * x is small, by a power series.
Authors
Stephen L. Moshier (original C code). Conversion to D by Don Clugston
License
Copyright © 1999-2018 by the D Language Foundation | Page generated by ddox.