In this section, we will consider various enhancements/generalizations of the linear regression model. We will begin with a piecewise linear regression model and then consider the polynomial regression extension.
spline refers to a thin strip of wood that can be easily bent along a curved line.
In the previous section, we made multiple transformations of the input variable
X with . In the Data Re-expression section of Chapter 4, Exploratory Analysis, we saw how a useful log transformation gave a better stem-and-leaf display than the original variable itself.
In many applications, it has been found that the ...