1 SUBROUTINE QUAD(X,Y,XA,YA) 2C 3C*** COMPUTES PARAMETERS FOR QUADRATIC EXTRAPOLATION 4C 5 DIMENSION X(3),Y(3),X2(3) 6 DATA DERIV/4HDERI/ 7 DET(A11,A12,A13,A21,A22,A23,A31,A32,A33)= A11*(A22*A33-A23*A32) - 8 1 A21*(A12*A33-A13*A32) + A31*(A12*A23-A13*A22) 9 DO 1000 I=1,3 10 1000 X2(I)=X(I)**2 11 D=DET(X2(1),X(1),1.,X2(2),X(2),1.,X2(3),X(3),1.) 12 A=DET(Y(1),X(1),1.,Y(2),X(2),1.,Y(3),X(3),1.) /D 13 B=DET(X2(1),Y(1),1.,X2(2),Y(2),1.,X2(3),Y(3),1.)/D 14 C=DET(X2(1),X(1),Y(1),X2(2),X(2),Y(2),X2(3),X(3),Y(3))/D 15C 16C ----TEST FOR TAKING DERIVATIVES 17C 18 IF(YA.EQ.DERIV)GO TO 1010 19C 20 YA=XA*(A*XA+B)+C 21 RETURN 22C 23 1010 YA=2.*A*XA+B 24 RETURN 25 END 26