Two potential "bugs"

[warmth88]

Hi Trevor,

Thanks for developing this tool. It has been really helpful for my research. As I'm using the "greater_is_better" feature of the code, I detected something abnormal originated from "genetic.py".

(1) if isinstance(self, RegressorMixin):
# Find the best individual in the final generation
self._program = self._programs[-1][np.argmin(fitness)]

This is only True when the best program we are seeking is the one that has lowest fitness, which is not the case for "greater_is_better".

(2) Similarly
if isinstance(self, TransformerMixin):
# Find the best individuals in the final generation
fitness = np.array(fitness)
hall_of_fame = fitness.argsort()[:self.hall_of_fame]

This would select top several programs that have lowest fitness instead of the highest.

[trevorstephens]

Yep, looks like a rather glaring bug, thank you for reporting. Looks like #40 addresses your first point. The second one might be implemented in the same PR. I'll ask @eggachecat if they can expand the PR to cover this as well.