*-- Author :   I.O.Skillicorn
      SUBROUTINE  FXFIT(X,Y,SIG,NDATA,A,MA,LISTA,MFIT,COVAR,NCVM,CHISQ)
      SAVE                                                              
C     ADDED FOR RESIDUALS                                                                                     
      COMMON /FPRES/NPLA,RES(100),IPRES(100),THET(100)                  
C     ADDED FOR SCALE FACTOR                                                                                  
      COMMON /FPSCAL/SF1,SF2,WZER(100)                                  
      PARAMETER (MMAX=100)                                              
      DIMENSION X(NDATA),Y(NDATA),SIG(NDATA),A(MA),LISTA(MA),           
     1 COVAR(NCVM,NCVM),BETA(MMAX),AFUNC(MMAX)                          
      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                                                           
      ELSEIF(IHIT.GT.1)THEN                                             
      WRITE(*,*)' IMPROPER SET IN LISTA'                                
      RETURN                                                            
      ENDIF                                                             
 12   CONTINUE                                                          
      IF(KK.NE.MA+1)THEN                                                
      WRITE(*,*)' IMPROPER SET IN LISTA '                               
      RETURN                                                            
      ENDIF                                                             
      DO 14 J=1,MFIT                                                    
      DO 13 K=1,MFIT                                                    
      COVAR(J,K)=0.                                                     
 13   CONTINUE                                                          
      BETA(J)=0.                                                        
 14   CONTINUE                                                          
      DO 18 I=1,NDATA                                                   
      CALL FFUNCS(I,AFUNC,MA)
      YM=Y(I)                                                           
      IF(MFIT.LT.MA)THEN                                                
      DO 15 J=MFIT+1,MA                                                 
      YM=YM-A(LISTA(J))*AFUNC(LISTA(J))                                 
 15   CONTINUE                                                          
      ENDIF                                                             
      SIG2I=1./SIG(I)**2                                                
      DO 17 J=1,MFIT                                                    
      WT=AFUNC(LISTA(J))*SIG2I                                          
      DO 16 K=1,J                                                       
      COVAR(J,K)=COVAR(J,K)+WT*AFUNC(LISTA(K))                          
 16   CONTINUE                                                          
      BETA(J)=BETA(J)+YM*WT                                             
 17   CONTINUE                                                          
 18   CONTINUE                                                          
      IF(MFIT.GT.1)THEN                                                 
      DO 21 J=2,MFIT                                                    
      DO 19 K=1,J-1                                                     
      COVAR(K,J)=COVAR(J,K)                                             
 19   CONTINUE                                                          
 21   CONTINUE                                                          
      ENDIF                                                             
      CALL FAUSSJ(COVAR,MFIT,NCVM,BETA,1,1)
      DO 22 J=1,MFIT                                                    
      A(LISTA(J))=BETA(J)                                               
 22   CONTINUE                                                          
      CHISQ=0.                                                          
C     ADDED FOR SCALE FACTOR 9/4/92                                                                           
      SF1=0.                                                            
      SF2=0.                                                            
      DO 24 I=1,NDATA                                                   
      CALL FFUNCS(I,AFUNC,MA)
      SUM=0.                                                            
      DO 23 J=1,MA                                                      
      SUM=SUM+A(J)*AFUNC(J)                                             
 23   CONTINUE                                                          
      CHISQ=CHISQ+((Y(I)-SUM)/SIG(I))**2                                
C     ADDITION  2/3/92                                                                                        
      RES(I)=(Y(I)-SUM)/SIG(I)                                          
      IF(I.GT.NPLA)GOTO24                                               
C     ADDITION  9/4/92                                                                                        
C     SF1=SF1+(Y(I)-WZER(I))*(SUM-WZER(I))/SIG(I)**2                                                          
C     SF2=SF2+(SUM-WZER(I))**2/SIG(I)**2                                                                      
C     Y-WZER  IS SIGNED DRIFT                                                                                 
      SF1=SF1+(Y(I)-WZER(I))/SIG(I)**2                                  
      SF2=SF2+(SUM-WZER(I))/SIG(I)**2                                   
 24   CONTINUE                                                          
C     CALL COVSRT(COVAR,NCVM,MA,LISTA,MFIT)                                                                   
      RETURN                                                            
      END                                                               
*