SUBROUTINE ZEFIT(DET,YDEF,NTAB,XTAB,DXTAB,SPOS,COEF,STATUS)
C
C Module Number: 13.8.1.2
C
C Module Name: ZEFIT
C
C Keyphrase:
C ----------
C  performs least squares fit to compute the HRS sample mapping function coef.
C
C Description:
C ------------
C Using a table containing x-deflections, diode on the edge, and edge location
C in sample units, a least squares fit is done to compute the coef. of the
C equation:
C                       s = s0 + b*(xdef-2048) + e*X
C where s is the photochode sample position
C       xdef is the x-deflection
C       X is the diode number
C       s0, b, e are the mapping coefficients
C
C
C FORTRAN Name: zefit.for
C
C
C Keywords of Accessed Files :
C --------------------------
C       NONE
C
C Modules Called:
C ---------------
C CDBS:
C       LFIT2
C SDAS:
C       UMSPUT
C
C History:
C --------
C Version       Date      Author        Description
C    1        10 MAR 86  D. Lindler     Design and coded
C    2        15 DEC 87  D. LINDLER     NEW SDAS I/O AND STANDARDS
C------------------------------------------------------------------------
C     INCLUDE FILE FOR THE IRAF77 FORTRAN INTERFACE TO THE IRAF VOS
C
C
C     FILE I/O ACCESS MODES
C
      INTEGER   RDONLY
      PARAMETER (RDONLY = 1)
      INTEGER   RDWRIT
      PARAMETER (RDWRIT = 2)
      INTEGER   WRONLY
      PARAMETER (WRONLY = 3)
      INTEGER   APPEND
      PARAMETER (APPEND = 4)
C
C     CODES FOR DATA TYPES
C
      INTEGER   TYBOOL
      PARAMETER (TYBOOL = 1)
      INTEGER   TYCHAR
      PARAMETER (TYCHAR = 2)
      INTEGER   TYINT
      PARAMETER (TYINT = 4)
      INTEGER   TYREAL
      PARAMETER (TYREAL = 6)
      INTEGER   TYDOUB
      PARAMETER (TYDOUB = 7)
C
C     UMSPUT DESTINATIONS -- CB, DAO, 4-SEP-87
C
      INTEGER STDOUT
      PARAMETER (STDOUT = 1)
      INTEGER STDERR
      PARAMETER (STDERR = 2)
C
C     UHDAS HEADER PARM TYPES -- CB, DAO, 5-SEP-87
C
      INTEGER GENHDR
      PARAMETER (GENHDR = 0)
      INTEGER IMSPEC
      PARAMETER (IMSPEC = 1)
C
C     THIS SECTION IS FOR PARAMETERS RELEVANT TO TABLE I/O.
C
C     THESE MAY BE SET BY UTPPTI AND/OR READ BY UTPGTI:
C
C                                       LENGTH OF ROW (UNIT = SIZE OF REAL)
      INTEGER   TBRLEN
      PARAMETER (TBRLEN = 1)
C                                       INCREASE ROW LENGTH
      INTEGER   TBIRLN
      PARAMETER (TBIRLN = 2)
C                                       NUMBER OF ROWS TO ALLOCATE
      INTEGER   TBALLR
      PARAMETER (TBALLR = 3)
C                                       INCREASE ALLOC NUM OF ROWS
      INTEGER   TBIALR
      PARAMETER (TBIALR = 4)
C                                       WHICH TYPE OF TABLE? (ROW OR COLUMN)
      INTEGER   TBWTYP
      PARAMETER (TBWTYP = 5)
C                                       MAXIMUM NUMBER OF USER PARAMETERS
      INTEGER   TBMXPR
      PARAMETER (TBMXPR = 6)
C                                       MAXIMUM NUMBER OF COLUMNS
      INTEGER   TBMXCL
      PARAMETER (TBMXCL = 7)
C                                       TYPE = ROW-ORDERED TABLE
      INTEGER   TBTYPR
      PARAMETER (TBTYPR = 11)
C                                       TYPE = COLUMN-ORDERED TABLE
      INTEGER   TBTYPC
      PARAMETER (TBTYPC = 12)
C
C     THESE MAY BE READ BY UTPGTI BUT MAY NOT BE SET:
C
C                                       NUMBER OF ROWS WRITTEN TO
      INTEGER   TBNROW
      PARAMETER (TBNROW = 21)
C
C     END IRAF77.INC
C
C INPUT:
C
        INTEGER         DET
C                                    ---> HRS DETECTOR NUMBER
        DOUBLE PRECISION YDEF
C                                    ---> Y-DEFLECTION
        INTEGER         NTAB
C                                    ---> NUMBER OF FOUND EDGE POSITIONS
        DOUBLE PRECISION XTAB(*)
C                                    ---> DIODE POSITIONS OF THE EDGE
        DOUBLE PRECISION DXTAB(*)
C                                    ---> X-DEFLECTIONS
        DOUBLE PRECISION SPOS(*)
C                                    ---> SAMPLE POSITION OF THE EDGES
C
C OUTPUT:
C
        DOUBLE PRECISION COEF(*)
C                                    ---> TABLE OF COEFFICIENTS
        INTEGER         STATUS
C                                    ---> ERROR STATUS
C
C LOCAL VARIABLES
C
        CHARACTER*130   MESS
C                                    ---> MESSAGE FOR TERMINAL
        DOUBLE PRECISION SIG(500),A(3),COVAR(3,3),CHISQ
        INTEGER LISTA(3),ISTAT
        CHARACTER*130   CONTXT
C
C FITTING FUNCTION
C
        EXTERNAL ZSFUNC
C
C  DATA DECLARATIONS
C
        DATA SIG/500*1.0/
        DATA LISTA/1,2,3/
C                                    ---> ERROR MESSAGE
C-----------------------------------------------------------------
        STATUS=0
C
C PERFORM LEAST SQUARES FIT
C
        CALL LFIT2(DXTAB,XTAB,SPOS,SIG,NTAB,A,3,LISTA,3,COVAR,3,
     *                  CHISQ,ZSFUNC,STATUS)
        IF(STATUS.NE.0)THEN
                CONTXT='Unable to fit sample coefficients'
                GOTO 999
        ENDIF
C
C COPY RESULTS TO OUTPUT TABLE
C
        COEF(1)=A(1)
C                                    ---> s0 coef.
        COEF(2)=DSQRT(COVAR(1,1))
        COEF(3)=A(2)
C                                    ---> b coef.
        COEF(4)=DSQRT(COVAR(2,2))
        COEF(5)=0.0
C                                    ---> c coef. (presently not used)
        COEF(6)=0.0
        COEF(7)=A(3)
C                                    ---> e coef.
        COEF(8)=DSQRT(COVAR(3,3))
        WRITE(MESS,99)DET,YDEF
99      FORMAT(' SAMPLE MAPPING COEFFICIENTS: DETECTOR',I2,
     *                    '   YDEF=',F6.0)
        CALL UMSPUT(MESS,STDOUT,0,ISTAT)
        WRITE(MESS,199)A(1),A(2),A(3)
199     FORMAT('    S0=',F7.2,'    B=',F8.5,'     E=',F8.5)
        CALL UMSPUT(MESS,STDOUT,0,ISTAT)
        GO TO 1000
999     CALL UMSPUT(CONTXT,STDOUT+STDERR,0,ISTAT)
1000    RETURN
        END