说明：  这个例子展示了如何应用偏最小二乘回归(plsr)和主成分回归(PCR),并讨论了两种方法的有效性。 本人亲测有效
(This example shows how to apply Partial Least Squares Regression (PLSR) and Principal Components Regression (PCR), and discusses the effectiveness of the two methods. PLSR and PCR are both methods to model a response variable when there are a large number of predictor variables, and those predictors are highly correlated or even collinear. Both methods construct new predictor variables, known as components,)