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diff --git a/2048/CH6/EX6.4/max_ex.sce b/2048/CH6/EX6.4/max_ex.sce
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+// To demonstrate the maximum property of ACF at zero lag, as discussed in Example 6.8 on page 175.
+// 6.4
+
+exec('label.sci',-1);
+
+S1 = [1 2 3 4]; 
+S2 = [1,-2,3,-4];
+S3 = [-1,-2,3,4];
+len = length(S1)-1; 
+xv = -len:len;
+m = 1;
+xi = rand(4,1,'normal');
+Spxi1 = S1 + m*xi';
+Spxi2 = S2 + m*xi';
+Spxi3 = S3 + m*xi';
+n = 1:length(S1);
+plot(n,Spxi1,'o-',n,Spxi2,'x--',n,Spxi3,'*:');
+label('',4,'n','y',4);
+ACF1 = xcov(Spxi1,"coeff");
+ACF2 = xcov(Spxi2,"coeff");
+ACF3 = xcov(Spxi3,"coeff");
+xset('window',1);
+a = gca();
+a.data_bounds = [-len -1; len 1];
+plot(xv,ACF1,'o-',xv,ACF2,'x--',xv,ACF3,'*:');
+label('',4,'Lag','ACF',4);