Below is the syntax highlighted version of LinearRegression.java from §9.7 Optimization.

/******************************************************************************
 * Compilation: javac LinearRegression.java StdIn.java
 * Execution: java LinearRegression < data.txt
 * 
 * Reads in a sequence of pairs of real numbers and computes the
 * best fit (least squares) line y = ax + b through the set of points.
 * Also computes the correlation coefficient and the standard errror
 * of the regression coefficients.
 *
 * Note: the two-pass formula is preferred for stability.
 *
 ******************************************************************************/
publicclassLinearRegression{
publicstaticvoidmain(String[] args){
int MAXN =1000;
int n =0;
double[] x =newdouble[MAXN];
double[] y =newdouble[MAXN];
// first pass: read in data, compute xbar and ybar
double sumx =0.0, sumy =0.0, sumx2 =0.0;
while(!StdIn.isEmpty()){
 x[n]= StdIn.readDouble();
 y[n]= StdIn.readDouble();
 sumx += x[n];
 sumx2 += x[n]* x[n];
 sumy += y[n];
 n++;
}
double xbar = sumx / n;
double ybar = sumy / n;
// second pass: compute summary statistics
double xxbar =0.0, yybar =0.0, xybar =0.0;
for(int i =0; i < n; i++){
 xxbar +=(x[i]- xbar)*(x[i]- xbar);
 yybar +=(y[i]- ybar)*(y[i]- ybar);
 xybar +=(x[i]- xbar)*(y[i]- ybar);
}
double beta1 = xybar / xxbar;
double beta0 = ybar - beta1 * xbar;
// print results
 StdOut.println("y = "+ beta1 +" * x + "+ beta0);
// analyze results
int df = n -2;
double rss =0.0;// residual sum of squares
double ssr =0.0;// regression sum of squares
for(int i =0; i < n; i++){
double fit = beta1*x[i]+ beta0;
 rss +=(fit - y[i])*(fit - y[i]);
 ssr +=(fit - ybar)*(fit - ybar);
}
double R2 = ssr / yybar;
double svar = rss / df;
double svar1 = svar / xxbar;
double svar0 = svar/n + xbar*xbar*svar1;
 StdOut.println("R^2 = "+ R2);
 StdOut.println("std error of beta_1 = "+ Math.sqrt(svar1));
 StdOut.println("std error of beta_0 = "+ Math.sqrt(svar0));
 svar0 = svar * sumx2 /(n * xxbar);
 StdOut.println("std error of beta_0 = "+ Math.sqrt(svar0));
 StdOut.println("SSTO = "+ yybar);
 StdOut.println("SSE = "+ rss);
 StdOut.println("SSR = "+ ssr);
}
}