REM   least squares curve fit program   "lstsq"    REV 11-98
DEFINT I,N,J
DIM X(500),Y(500),XRAW(500),YRAW(500),AF(5),BF(5)
COLOR 15,1,1
CLS
PRINT "MULTIFUNCTION LEAST SQUARES CURVE FIT        Copyright 1998 by D. Raymer"
PRINT
PRINT "INPUT DATA POINTS  X,Y       RETURN TWICE TO END INPUT"
FOR I=1 TO 500
INPUT "       ",XRAW(I),YRAW(I)
IF I>1 THEN
   IF XRAW(I)=0 AND YRAW(I)=0 AND XRAW(I-1)=0 AND YRAW(I-1)=0 THEN EXIT FOR
   END IF
NEXT I
N=I-2
54 CLS
PRINT "RAYMER'S LEAST SQUARES CURVE FIT RESULTS "
FOR J=1 TO 5

FOR I=1 TO n
X(I)=XRAW(I)
Y(I)=YRAW(I)
IF (J=2 OR J=4) THEN Y(I)=LOG10(Y(I))
IF(J=3 OR J=4) THEN X(I)=LOG10(X(I))
IF(J=5) THEN X(I)=X(I)*X(I)
IF(J=5) THEN Y(I)=Y(I)*Y(I)
NEXT I

SX2=0
SY2=0
SX=0
SY=0
SXY=0
FOR I=1 TO N
SX2=SX2+X(I)*X(I)
SY2=SY2+Y(I)*Y(I)
SX=SX+X(I)
SY=SY+Y(I)
SXY=SXY+X(I)*Y(I)
NEXT I
D=SX2-SX*SX/N
A=(SX2*SY-SX*SXY)/(N*D)
B=(SXY-SX*SY/N)/D
IF (SX2-SX*SX/N)*(SY2-SY*SY/N)>0. THEN
  CORELAT=(SXY-SX*SY/N)/SQR((SX2-SX*SX/N)*(SY2-SY*SY/N))
  ELSE
  CORELAT=-999
  END IF
AF(J)=A
BF(J)=B
IF(J=1) THEN PRINT "linear :     y= a+b*x         ";
IF(J=2) THEN PRINT "log y vs x : y= 10^(a+b*x )   ";
IF(J=3) THEN PRINT "log x vs y : y= a+b*log10(x)  ";
IF(J=4) THEN PRINT "log-log :    y= (10^a)*(x^b)  ";
IF(J=5) THEN PRINT "elliptic:    y= sqrt(a+b*x^2) ";
PRINT " a= ";A;" b= ";B;" Cor.= ";CORELAT
NEXT J
PRINT
PRINT "   Actual X   Actual Y    Y-linear   Y-log y    Y-logx     Y-loglog   Y-elliptic"
IDUM=8
FOR I=1 TO N
IDUM=IDUM+1
IF IDUM>23 THEN
   LOCATE 25,1
   PRINT "Copy if desired.  Press any key to continue";
   WHILE NOT INSTAT : WEND:  A$=INKEY$
   CLS
   IDUM=1
   END IF
X(I)=XRAW(I)
Y(I)=YRAW(I)
PRINT USING ("#####.#####");XRAW(I);YRAW(I);(AF(1)+BF(1)*X(I));(10^(AF(2)+BF(2)*X(I))); _
  (AF(3)+BF(3)*log10(X(I)));(10^AF(4)*X(I)^BF(4));(sqr(AF(5)+BF(5)*X(I)^2))

NEXT I

LOCATE 25,1
PRINT "Done! Press R to revise inputs and recalculate.  Press another key to Exit.";
WHILE NOT INSTAT : WEND
A$=INKEY$
IF A$="R" OR A$="r" THEN
   CLS
   PRINT "INPUT NEW X,Y POINTS.  RETURN TO LEAVE BOTH X & Y UNCHANGED."
   FOR I=1 TO N
    PRINT "CURRENT:  ",XRAW(I);", ",YRAW(I)," ";
    INPUT "INPUT NEW X,Y:  ",XINPT,YINPT
    IF XINPT*YINPT<>0. THEN
     XRAW(I)=XINPT
     YRAW(I)=YINPT
     END IF
    NEXT I
   GOTO 54
   END IF
END