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decuslib20-02
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decus/20-0026/besj.doc
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SUBROUTINE BESJ
PURPOSE
COMPUTE THE J BESSEL FUNCTION FOR A GIVEN ARGUMENT AND ORDER
USAGE
CALL BESJ(X,N,BJ,D,IER)
DESCRIPTION OF PARAMETERS
X -THE ARGUMENT OF THE J BESSEL FUNCTION DESIRED
N -THE ORDER OF THE J BESSEL FUNCTION DESIRED
BJ -THE RESULTANT J BESSEL FUNCTION
D -REQUIRED ACCURACY
IER-RESULTANT ERROR CODE WHERE
IER=0 NO ERROR
IER=1 N IS NEGATIVE
IER=2 X IS NEGATIVE OR ZERO
IER=3 REQUIRED ACCURACY NOT OBTAINED
IER=4 RANGE OF N COMPARED TO X NOT CORRECT (SEE REMARKS)
REMARKS
N MUST BE GREATER THAN OR EQUAL TO ZERO, BUT IT MUST BE
LESS THAN
20+10*X-X** 2/3 FOR X LESS THAN OR EQUAL TO 15
90+X/2 FOR X GREATER THAN 15
SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
NONE
METHOD
RECURRENCE RELATION TECHNIQUE DESCRIBED BY H. GOLDSTEIN AND
R.M. THALER,'RECURRENCE TECHNIQUES FOR THE CALCULATION OF
BESSEL FUNCTIONS',M.T.A.C.,V.13,PP.102-108 AND I.A. STEGUN
AND M. ABRAMOWITZ,'GENERATION OF BESSEL FUNCTIONS ON HIGH
SPEED COMPUTERS',M.T.A.C.,V.11,1957,PP.255-257