# SLATEC Routines --- ASYIK ---

```*DECK ASYIK
SUBROUTINE ASYIK (X, FNU, KODE, FLGIK, RA, ARG, IN, Y)
C***BEGIN PROLOGUE  ASYIK
C***SUBSIDIARY
C***PURPOSE  Subsidiary to BESI and BESK
C***LIBRARY   SLATEC
C***TYPE      SINGLE PRECISION (ASYIK-S, DASYIK-D)
C***AUTHOR  Amos, D. E., (SNLA)
C***DESCRIPTION
C
C                    ASYIK computes Bessel functions I and K
C                  for arguments X.GT.0.0 and orders FNU.GE.35
C                  on FLGIK = 1 and FLGIK = -1 respectively.
C
C                                    INPUT
C
C      X    - argument, X.GT.0.0E0
C      FNU  - order of first Bessel function
C      KODE - a parameter to indicate the scaling option
C             KODE=1 returns Y(I)=        I/SUB(FNU+I-1)/(X), I=1,IN
C                    or      Y(I)=        K/SUB(FNU+I-1)/(X), I=1,IN
C                    on FLGIK = 1.0E0 or FLGIK = -1.0E0
C             KODE=2 returns Y(I)=EXP(-X)*I/SUB(FNU+I-1)/(X), I=1,IN
C                    or      Y(I)=EXP( X)*K/SUB(FNU+I-1)/(X), I=1,IN
C                    on FLGIK = 1.0E0 or FLGIK = -1.0E0
C     FLGIK - selection parameter for I or K function
C             FLGIK =  1.0E0 gives the I function
C             FLGIK = -1.0E0 gives the K function
C        RA - SQRT(1.+Z*Z), Z=X/FNU
C       ARG - argument of the leading exponential
C        IN - number of functions desired, IN=1 or 2
C
C                                    OUTPUT
C
C         Y - a vector whose first in components contain the sequence
C
C     Abstract
C         ASYIK implements the uniform asymptotic expansion of
C         the I and K Bessel functions for FNU.GE.35 and real
C         X.GT.0.0E0. The forms are identical except for a change
C         in sign of some of the terms. This change in sign is
C         accomplished by means of the flag FLGIK = 1 or -1.
C