機器學習中：過擬合（overfitting）和欠擬合（underfitting）
阿新 • • 發佈：2019-02-02
Underfitting is easy to check as long as you know what the cost function measures. The definition of the cost function in linear regression is half
the mean squared error. That is, if the mean error for each point is z, then the cost will be0.5z2. So if your output ranges from, say, 100 to 1000, and your cost is 1, then the mean error would be 1.4, which represents a mean
error of anywhere from 1.4% to 0.14%, and that may be good enough. If, however, your cost is 50, then the mean error would be 10, which is anywhere from 10% to 1%, which is probably bad.