SLATEC Routines --- ZRATI ---

*DECK ZRATI
      SUBROUTINE ZRATI (ZR, ZI, FNU, N, CYR, CYI, TOL)
C***BEGIN PROLOGUE  ZRATI
C***SUBSIDIARY
C***PURPOSE  Subsidiary to ZBESH, ZBESI and ZBESK
C***LIBRARY   SLATEC
C***TYPE      ALL (CRATI-A, ZRATI-A)
C***AUTHOR  Amos, D. E., (SNL)
C***DESCRIPTION
C
C     ZRATI COMPUTES RATIOS OF I BESSEL FUNCTIONS BY BACKWARD
C     RECURRENCE.  THE STARTING INDEX IS DETERMINED BY FORWARD
C     RECURRENCE AS DESCRIBED IN J. RES. OF NAT. BUR. OF STANDARDS-B,
C     MATHEMATICAL SCIENCES, VOL 77B, P111-114, SEPTEMBER, 1973,
C     BESSEL FUNCTIONS I AND J OF COMPLEX ARGUMENT AND INTEGER ORDER,
C     BY D. J. SOOKNE.
C
C***SEE ALSO  ZBESH, ZBESI, ZBESK
C***ROUTINES CALLED  ZABS, ZDIV
C***REVISION HISTORY  (YYMMDD)
C   830501  DATE WRITTEN
C   910415  Prologue converted to Version 4.0 format.  (BAB)
C***END PROLOGUE  ZRATI