*  This is file PRESSURE.SAS  ; 
options noovp; 
title 'Baroreceptor contol of blood pressure--nonlinear regresssion'; 
*  Normal data set  (Data in Table C-20) ; 
DATA normal; 
     infile presnorm; 
     input N P; 
*  Hypertensive data set  (Data in Table C-21) ; 
DATA hyper; 
     infile preshypr; 
     input N P; 
*  Fit simple, MIN, MAX parameterization to normal data   ; 
proc NLIN data=normal METHOD=MARQUARDT; 
        parameters Nmax=90 Nmin=5 C=4 D=-.1; 
        model N=Nmax-(Nmax-Nmin)/(1+exp(-(C+D*P))); 
                X=exp(-(C+D*P)); 
                DER.Nmax=1-1/(1+X); 
                DER.Nmin=1/(1+X); 
                DER.C=-(Nmax-Nmin)*X/(1+X)**2; 
                DER.D=P*DER.C; 
        output OUT=Plot1 PREDICTED=Nhat RESIDUAL=resid STUDENT=stdres
                  H=hat; 
proc PLOT data=Plot1; 
        plot N*P='O' Nhat*P='P' / OVERLAY VPOS=25; 
        plot resid*P / VREF=0 VPOS=25; 
        plot resid*Nhat / VREF=0 VPOS=25; 
proc PRINT data=Plot1; 
     var N Nhat resid stdres hat; 
*  Fit simple, MIN, MAX parameterization to hypertensive data   ; 
proc NLIN data=hyper METHOD=MARQUARDT; 
        parameters Nmax=70 Nmin=5 C=4 D=-.1; 
        model N=Nmax-(Nmax-Nmin)/(1+exp(-(C+D*P))); 
                X=exp(-(C+D*P)); 
                DER.Nmax=1-1/(1+X); 
                DER.Nmin=1/(1+X); 
                DER.C=-(Nmax-Nmin)*X/(1+X)**2; 
                DER.D=P*DER.C; 
        output OUT=Plot2 PREDICTED=Nhat RESIDUAL=resid STUDENT=stdres
                  H=hat; 
proc PLOT data=Plot2; 
        plot N*P='O' Nhat*P='P' / OVERLAY VPOS=25; 
        plot resid*P / VREF=0 VPOS=25; 
        plot resid*Nhat / VREF=0 VPOS=25; 
proc PRINT data=Plot2; 
     var N Nhat resid stdres hat; 
*  Fit alternative parameterization to normal data   ; 
proc NLIN data=normal METHOD=MARQUARDT; 
        parameters Nmin=0 Nmax=90 Phalf=100 s=1.5; 
        model N=Nmin+(Nmax-Nmin)/(1+exp(4*s*(Phalf-P)/(Nmax-Nmin))); 
        DeltaN=Nmax-Nmin; 
        DeltaP=Phalf-P; 
        X = exp(4*s*DeltaP/DeltaN); 
        X1=1+X; 
*NOTE The following line is in error in the book;
        DER.Nmax=(X1+X*4*s*DeltaP/DeltaN)/X1**2; 
        DER.Nmin=1-(X1+X*4*s*DeltaP/DeltaN)/X1**2; 
        DER.Phalf=-X*4*s/X1**2; 
        DER.s=-X*4*DeltaP/X1**2; 
        output OUT=Plot3 PREDICTED=Nhat RESIDUAL=resid STUDENT=stdres
                  H=hat; 
proc PLOT data=Plot3; 
        plot N*P='O' Nhat*P='P' / OVERLAY VPOS=25; 
        plot resid*P / VREF=0 VPOS=25; 
        plot resid*Nhat / VREF=0 VPOS=25; 
proc PRINT data=Plot3; 
        var N Nhat resid stdres hat; 
*  Fit alternative parameterization to hypertensive data   ; 
proc NLIN data=hyper METHOD=MARQUARDT; 
        parameters Nmin=0 Nmax=70 Phalf=100 s=1.5; 
        model N=Nmin+(Nmax-Nmin)/(1+exp(4*s*(Phalf-P)/(Nmax-Nmin))); 
        DeltaN=Nmax-Nmin; 
        DeltaP=Phalf-P; 
        X = exp(4*s*DeltaP/DeltaN); 
        X1=1+X; 
*NOTE The following line is in error in the book;
        DER.Nmax=(X1+X*4*s*DeltaP/DeltaN)/X1**2; 
        DER.Nmin=1-(X1+X*4*s*DeltaP/DeltaN)/X1**2; 
        DER.Phalf=-X*4*s/X1**2; 
        DER.s=-X*4*DeltaP/X1**2; 
        output OUT=Plot4 PREDICTED=Nhat RESIDUAL=resid STUDENT=stdres
                  H=hat; 
proc PLOT data=Plot4; 
        plot N*P='O' Nhat*P='P' / OVERLAY VPOS=25; 
        plot resid*P / VREF=0 VPOS=25; 
        plot resid*Nhat / VREF=0 VPOS=25; 
proc PRINT data=Plot4; 
     var N Nhat resid stdres hat;