为什么我们在交叉评分前使用“”（负号）

Question

为什么我们使用“-cross\u val\u score”而不是cross\u val\u score

cv_mae = -cross_val_score(lm,
                         x_train,y_train,
                         cv=10,
                         scoring='neg_mean_absolute_error')

Answer 1

这是由于scikit-learn中的一个约定：

All scorer objects follow the convention that higher return values are better than lower return values. Thus metrics which measure the distance between the model and the data, like metrics.mean_squared_error, are available as neg_mean_squared_error which return the negated value of the metric.

（引自here）

由于您的cross_val_score返回负的MAE（请参见您将scoring='neg_mean_absolute_error'作为参数传递），因此您需要负号来获得实际的MAE