| The R-square fitness function of APS 3.0 is, as expected, based on the standard
R-square, which returns the square of the Pearson product moment correlation coefficient. The Pearson product moment correlation coefficient is a dimensionless index that ranges from -1 to 1 and reflects the extent of a linear relationship between two data sets. The Pearson product moment correlation coefficient Ri of an individual program i is evaluated by the equation:
where P(ij) is the value predicted by the individual program
i for fitness case j (out of n fitness cases);
and Tj is the target value for fitness case j. fi = 1000*Ri*Ri which allows a fairer distribution of fitnesses for selection. |
