mrqmin.f

      SUBROUTINE MRQMIN(X,Y,SIG,NDATA,A,MA,LISTA,MFIT,
     *    COVAR,ALPHA,NCA,CHISQ,FUNCS,ALAMDA)
      PARAMETER (MMAX=20)
      DIMENSION X(NDATA),Y(NDATA),SIG(NDATA),A(MA),LISTA(MA),
     *  COVAR(NCA,NCA),ALPHA(NCA,NCA),ATRY(MMAX),BETA(MMAX),DA(MMAX)
      IF(ALAMDA.LT.0.)THEN
        KK=MFIT+1
        DO 12 J=1,MA
          IHIT=0
          DO 11 K=1,MFIT
            IF(LISTA(K).EQ.J)IHIT=IHIT+1
11        CONTINUE
          IF (IHIT.EQ.0) THEN
            LISTA(KK)=J
            KK=KK+1
          ELSE IF (IHIT.GT.1) THEN
            PAUSE 'Improper permutation in LISTA'
          ENDIF
12      CONTINUE
        IF (KK.NE.(MA+1)) PAUSE 'Improper permutation in LISTA'
        ALAMDA=0.001
        CALL MRQCOF(X,Y,SIG,NDATA,A,MA,LISTA,MFIT,ALPHA,BETA,NCA,CHISQ,F
     *UNCS)
        OCHISQ=CHISQ
        DO 13 J=1,MA
          ATRY(J)=A(J)
13      CONTINUE
      ENDIF
      DO 15 J=1,MFIT
        DO 14 K=1,MFIT
          COVAR(J,K)=ALPHA(J,K)
14      CONTINUE
        COVAR(J,J)=ALPHA(J,J)*(1.+ALAMDA)
        DA(J)=BETA(J)
15    CONTINUE
      CALL GAUSSJ(COVAR,MFIT,NCA,DA,1,1)
      IF(ALAMDA.EQ.0.)THEN
        CALL COVSRT(COVAR,NCA,MA,LISTA,MFIT)
        RETURN
      ENDIF
      DO 16 J=1,MFIT
        ATRY(LISTA(J))=A(LISTA(J))+DA(J)
16    CONTINUE
      CALL MRQCOF(X,Y,SIG,NDATA,ATRY,MA,LISTA,MFIT,COVAR,DA,NCA,CHISQ,FU
     *NCS)
      IF(CHISQ.LT.OCHISQ)THEN
        ALAMDA=0.1*ALAMDA
        OCHISQ=CHISQ
        DO 18 J=1,MFIT
          DO 17 K=1,MFIT
            ALPHA(J,K)=COVAR(J,K)
17        CONTINUE
          BETA(J)=DA(J)
          A(LISTA(J))=ATRY(LISTA(J))
18      CONTINUE
      ELSE
        ALAMDA=10.*ALAMDA
        CHISQ=OCHISQ
      ENDIF
      RETURN
      END