public double slope() {
        return beta;
    }
Returns the slope &beta; of the best of the best-fit line <em>y</em> = &alpha; + &beta; <em>x</em>.
@return the slope &beta; of the best-fit line <em>y</em> = &alpha; + &beta; <em>x</em>
library/src/main/java/com/lorentzos/flingswipe/LinearRegression.java