SUBROUTINE LINFIT
      COMMON /FIT/X,Y,SIGMAY,NPTS,MODE,A,SIGMAA,B,SIGMAB,R,SCALEX,SCALEY
      INTEGER NPTS,MODE
      DOUBLE PRECISION X,Y,SIGMAY,A,SIGMAA,B,SIGMAB,R
      DOUBLE PRECISION SUM,SUMX,SUMY,SUMX2,SUMXY,SUMY2
      DOUBLE PRECISION XI,YI,WEIGHT,DELTA,VARNCE,SCALEX,SCALEY
      DIMENSION X(50),Y(50),SIGMAY(50)
11    SUM=0.
      SUMX=0.
      SUMY=0.
      SUMX2=0.
      SUMXY=0.
      SUMY2=0.
21    DO 50 I=1,NPTS
      XI=X(I)/SCALEX
      YI=Y(I)/SCALEY
      IF (MODE) 31,36,38
31    IF (YI)34,36,32
32    WEIGHT=1./YI
      GOTO 41
34    WEIGHT=1./(-YI)
      GOTO 41
36    WEIGHT=1.
      GOTO 41
38    WEIGHT=1./SIGMAY(I)**2
41    SUM=SUM+WEIGHT
42    SUMX=SUMX+WEIGHT*XI
      SUMY=SUMY+WEIGHT*YI
      SUMX2=SUMX2+WEIGHT*XI*XI
      SUMXY=SUMXY+WEIGHT*XI*YI
      SUMY2=SUMY2+WEIGHT*YI*YI
50    CONTINUE
51    DELTA=SUM*SUMX2-SUMX*SUMX
      A=(SUMX2*SUMY-SUMX*SUMXY)/DELTA
      B=(SUMXY*SUM-SUMX*SUMY)/DELTA
61    IF (MODE)62,64,62
62    VARNCE=1.
      GOTO 67
64    C=NPTS-2
      VARNCE=(SUMY2+A*A*SUM+B*B*SUMX2-2.*(A*SUMY+B*SUMXY-A*B*SUMX))/C
67    SIGMAA=DSQRT(VARNCE*SUMX2/DELTA)
68    SIGMAB=DSQRT(VARNCE*SUM/DELTA)
71    R=(SUM*SUMXY-SUMX*SUMY)/(DSQRT(DELTA)*DSQRT(SUM*SUMY2-SUMY*SUMY))
      A=A*SCALEY
      SIGMAA=SIGMAA*SCALEY
      B=B*SCALEY/SCALEX
      SIGMAB=SIGMAB*SCALEY/SCALEX
      RETURN
      END