Date: Sun, 12 Feb 95 19:04:02 +0000

Here is the transcription of algorithm #6 of Collected
Algorithms from CACM.

	I substituted greek letters by their names, the multiplicative
operator by * and the potentiation (x raised to y) by ^ (x ^ y).

				jr

			Jose R. Valverde
		European Bioinformatics Institute
			txomsy@ebi.ac.uk


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6. BESSEL FUNCTION I, ASYMPTOTIC EXPANSION
   Dorothea S. Clarke
   General Electric Co., FPLD, Cincinnati 15, Ohio

comment	Compute the Bessel Function In(X) when n and X
	are within the bounds of the asymptotic expansion.
	The procedure calling statement gives n, X and an
	absolute tolerance delta for determining the point at
	which the terms of the summation become in-
	significant;

procedure	I(n, X, delta) =: (IA)
begin
I:		r := 1 ; pe := (4 * (n^2) - 1) / (8 * X)
		  sum := - pe
Repeat:		r := r + 1
		pe := pe * (((2 * n)^2) - ((2 * r - 1)^2)) / (r * 8 * X)
if		(delta < abs(pe))
begin		sum := sum + ((-1)^r) * pe ; go to Repeat end
		IA := (1 + sum) * (exp(X) / sqrt(2 * PI * X))
		  return
end