CTITLESAVFFK  -- COMPUTE INSTANTANEOUS AMPLITUDE
C***********************************************************************
C                 COPYRIGHT ATLANTIC RICHFIELD COMPANY 1991            *
C***********************************************************************
CA    AUTHOR      BRUCE VER WEST
CA    DESIGNER    BRUCE VER WEST
CA    LANGUAGE    FORTRAN 77
CA    SYSTEM      CRAY / IBM
CA    WRITTEN     07/01/87
C     REVISED     MM-DD-YY                                              00070009
CA                                                                      00080009
CA    THE PURPOSE OF THIS SUBROUTINE IS TO COMPUTE THE INSTANTANEOUS    00080009
CA    AMPLITUDE OF THE SEMBLENCE TRACE IN THE PROCESS VFFK.             00080009
CA                                                                      00080009
CA                                                                      00080009
CA    SUBROUTINE SAVFFK(OTR,A,MAG,NT,NW,NWD2,NWD21,IPR,IABORT)          00080009
CA                                                                      00080009
CA    ARGUMENTS:                                                        00080009
CA                                                                      00080009
CA    OTR          INPUT/         REAL ARRARY CONTAINING THE INSTAN-    00080009
CA                 OUTPUT         TANEOUS AMPLITUDE                     00080009
CA                                                                      00080009
CA    A            OUTPUT         COMPLEX ARRAY USED IN COMPUTING       00080009
CA                                THE FFT                               00080009
CA                                                                      00080009
CA    MAG          INPUT          THE POWER OF TWO LENGTH FOR THE       00080009
CA                                FFT ROUTINE S2FFT2                    00080009
CA                                                                      00080009
CA    NT           INPUT          THE NUMBER OF TRACE SAMPLES           00080009
CA                                                                      00080009
CA    NW           INPUT          THE NUMBER OF FREQUENCIES RESULTING   00080009
CA                                FROM THE FFT INCLUDING POSITIVE AND   00080009
CA                                NEGATIVE VALUES                       00080009
CA                                                                      00080009
CA    NWD2         INPUT          THE NUMBER OF NON-NEGATIVE FREQUENCIES00080009
CA                                                                      00080009
CA    NWD21        INPUT          THE INDEX POSITIVE OF THE NYQUIST FRE-00080009
CA                                QUENCY                                00080009
CA                                                                      00080009
CA    IPR          INPUT          SPARC LOGICAL UNIT NUMBER FOR PRINT   00080009
CA                                                                      00080009
CA    IABORT       OUTPUT         FLAG WHICH IF SET TO YES WILL ABORT   00080009
CA                                THE PROCESS UPON EXIT FROM THE SUB-   00080009
CA                                ROUTINE                               00080009
CA                                                                      00080009
C***********************************************************************

      SUBROUTINE SAVFFK(OTR,A,MAG,NT,NW,NWD2,NWD21,IPR,IABORT)

      DIMENSION OTR(*)
      COMPLEX A(*)
      INTEGER YES,NO
      DATA     YES    /0/
      DATA     NO     /1/
C
      DO 10 IW=1,NW
   10 A(IW)=0.
      CALL SCOPY(NT,OTR,1,A,2)
C
C     CALL CFFT2(0,+1,NW,A,WORKT,A)
      CALL S2FFT2(MAG,A,             *999)
C
      DO 100 IW=NWD21,NW
  100 A(IW)=0.
      CALL CSSCAL(NWD2,2.,A(2),1)
C
C     CALL CFFT2(0,-1,NW,A,WORKT,A)
      CALL S2FFI2(MAG,A,             *999)
      DO 200 IT=1,NT
  200 OTR(IT)=SQRT(REAL(A(IT))**2+AIMAG(A(IT))**2)
C 200 OTR(IT)=SQRT(REAL(A(IT))**2+AIMAG(A(IT))**2)/FLOAT(NW)
C
      GO TO 300
  999 IABORT = YES
      WRITE (IPR,998)
  998 FORMAT(' *****  FFT TABLE LENGTH EXCEEDED IN S2FFT2 *****')
  300 RETURN
      END