Apply spline regression to the geophones data frame. Specifically, regress thickness against distance, and check the fits of 4-, 5- and 6-degree-of-freedom cases. Which case gives the best fit to the...

Apply spline regression to the geophones data frame. Specifically, regress thickness against distance, and check the fits of 4-, 5- and 6-degree-of-freedom cases. Which case gives the best fit to the data? How does this fitted curve compare with the polynomial curves obtained in the previous exercise? Calculate pointwise confidence bounds for the 5-degree-of-freedom case.