PROGRAM BT5_11
	DIMENSION X(100),Y(100)

	OPEN(1,FILE='C:\MASTER\G_TR\BaiTap~1\New\BANG15.TXT')
	READ(1,*)
	READ(1,*) N
	READ(1,*) ((X(I),Y(I)),I=1,N)
	R=HSTQ(X,Y,N)
	ETA=TYSOTQ(X,Y,N)
	WRITE(*,*)' TY SO TUONG QUAN = ',ETA
	WRITE(*,*)' HE SO TUONG QUAN = ',R

	END

	FUNCTION HSTQ(X,Y,N)
! HAM NAY TINH HE SO TUONG QUAN GIUA HAI BIEN X VA Y
! INPUT: + X MANG MOT CHIEU KICH THUOC N CHUA SO LIEU CUA X
!        + Y MANG MOT CHIEU KICH THUOC N CHUA SO LIEU CUA Y
!        + N DUNG LUONG MAU
! OUTPUT: HE SO TUONG QUAN R GIUA X VA Y
!
	DIMENSION X(N),Y(N)
	TBX=0.0
	TBY=0.0
	SX=0.0
	SY=0.0
	RXY=0.0
	DO I=1,N
	   TBX=TBX+X(I)
	   TBY=TBY+Y(I)
	   SX=SX+X(I)*X(I)
	   SY=SY+Y(I)*Y(I)
	   RXY=RXY+X(I)*Y(I)
	ENDDO
	TBX=TBX/REAL(N)
	TBY=TBY/REAL(N)
	SX=SQRT(SX/REAL(N))
	SY=SQRT(SY/REAL(N))
	RXY=RXY/REAL(N)-TBX*TBY
	HSTQ=RXY/SX/SY
	RETURN
	END

	FUNCTION TYSOTQ(X,Y,N)
! CHUONG TRINH NAY TINH TY SO TUONG QUAN GIUA HAI BIEN X VA Y
! INPUT: + X MANG MOT CHIEU KICH THUOC N CHUA SO LIEU CUA X
!        + Y MANG MOT CHIEU KICH THUOC N CHUA SO LIEU CUA Y
!        + N DUNG LUONG MAU
! OUTPUT: TY SO TUONG QUAN ETA GIUA X VA Y
!
	DIMENSION X(N),Y(N),TSO(N/2,N/2)
	DIMENSION XC(N/2),YC(N/2),TSX(N/2),TSY(N/2),A(N/2)
	LOGICAL LX,LY

	XMIN=X(1)
	XMAX=X(1)
	YMIN=Y(1)
	YMAX=Y(1)
	DO I=2,N
	IF (X(I).LT.XMIN) XMIN=X(I)
	IF (X(I).GT.XMAX) XMAX=X(I)
	IF (Y(I).LT.YMIN) YMIN=Y(I)
	IF (Y(I).GT.YMAX) YMAX=Y(I)
	ENDDO
	XMIN=1.0*INT(XMIN)
	YMIN=1.0*INT(YMIN)
	XMAX=1.0*INT(XMAX)+1.0
	YMAX=1.0*INT(YMAX)+1.0

	NSTEP=INT(5.0*LOG10(REAL(N)))+1
	STEPX=(XMAX-XMIN)/REAL(NSTEP)
	STEPY=(YMAX-YMIN)/REAL(NSTEP)

! TINH BANG PHAN BO TAN SO HAI CHIEU (TSO)
	DO KX=1,NSTEP
	   AX=XMIN+REAL(KX-1)*STEPX
	   BX=AX+STEPX

	   DO KY=1,NSTEP
	      AY=YMIN+REAL(KY-1)*STEPY
	      BY=AY+STEPY
	      TSO(KX,KY)=0.0

	      DO I=1,N
	         LX=(X(I).GE.AX).AND.(X(I).LT.BX)
	         LY=(Y(I).GE.AY).AND.(Y(I).LT.BY)
	         IF (LX.AND.LY) THEN
	            TSO(KX,KY)=TSO(KX,KY)+1.0
	         ENDIF
	      ENDDO
         ENDDO
	ENDDO

	XMIN=XMIN-STEPX/2.0
	YMIN=YMIN-STEPY/2.0

! TINH CAC TRI SO GIUA CUA X (XC) VA Y (YC)
	DO KX=1,NSTEP
	   XC(KX)=XMIN+REAL(KX)*STEPX
	   TSX(KX)=0.0
	   DO KY=1,NSTEP
	      TSX(KX)=TSX(KX)+TSO(KX,KY)
	   ENDDO
	ENDDO

	DO KY=1,NSTEP
	   YC(KY)=YMIN+REAL(KY)*STEPY
	   TSY(KY)=0.0
	   DO KX=1,NSTEP
	      TSY(KY)=TSY(KY)+TSO(KX,KY)
	   ENDDO
	ENDDO

!	WRITE(*,*)HSTQ(XC,YC,NSTEP)
!	WRITE(*,'("       ",12F5.1)')(XC(I),I=1,NSTEP)
!	DO I=1,NSTEP
!	WRITE(*,'(F7.2,12F5.0)')YC(I),(TSO(I,J),J=1,NSTEP)
!	ENDDO

! TINH CAC A(I)
	DO KX=1,NSTEP
	   A(KX)=0.0
	   DO KY=1,NSTEP
	      A(KX)=A(KX)+TSO(KX,KY)*YC(KY)
	   ENDDO
	ENDDO

! TINH D,B,C
	D=0.0
	B=0.0
	C=0.0
	DO KX=1,NSTEP
	   D=D+(A(KX)**2)/TSX(KX)
	ENDDO
	DO KY=1,NSTEP
	   B=B+TSY(KY)*YC(KY)
	   C=C+TSY(KY)*YC(KY)**2
	ENDDO

! TINH TY SO TUONG QUAN
	B=B**2/REAL(N)
	ETA=(D-B)/(C-B)
	TYSOTQ=ETA
	RETURN
	END