Hypergeometric function using Euler's integral representation

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Description

Hypergeometric function using Euler's integral representation, evaluated using numerical contour integrals.

Usage

1
f15.3.1(A, B, C, z, h = 0)

Arguments

A,B,C

Parameters

z

Primary complex argument

h

specification for the path to be taken; see details

Details

Argument h specifies the path to be taken (the path has to avoid the point 1/z). If h is real and of length 1, the path taken comprises two straight lines: one from 0 to 0.5+hi and one from 0.5+hi to 1 (if h=0 the integration is performed over a single segment).

Otherwise, the integration is performed over length(h)+1 segments: 0 to h[1], then h[i] to h[i+1] for 1 <= i <= n-1 and finally h[n] to 1.

See examples and notes sections below.

Note

The Mellin-Barnes form is not yet coded up.

Author(s)

Robin K. S. Hankin

References

M. Abramowitz and I. A. Stegun 1965. Handbook of mathematical functions. New York: Dover

See Also

hypergeo

Examples

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# For |z| <1 the path can be direct:
f15.3.1(2,1,2,-1/2) -2/3

# cf identity 07.23.03.0046.01 of Hypergeometric2F1.pdf with b=1




f <- function(h){f15.3.1(1,2,3, z=2, h=h)}

# Winding number [around 1/z] matters:
f(0.5)
f(c(1-1i, 1+1i, -2i))

# Accuracy isn't too bad; compare numerical to analytical result :
f(0.5) - (-1+1i*pi/2)