public double predict(double x) {
        return beta*x + alpha;
    }
Returns the expected response <tt>y</tt> given the value of the predictor
   variable <tt>x</tt>.
@param x the value of the predictor variable
@return the expected response <tt>y</tt> given the value of the predictor
   variable <tt>x</tt>
library/src/main/java/com/lorentzos/flingswipe/LinearRegression.java