Apply the penalized spline to the geophones data using the default arguments in mgcv’s s() function. Is this a satisfactory fit to the data? The argument k controls the number of knots. Try setting k...

Apply the penalized spline to the geophones data using the default arguments in mgcv’s s() function. Is this a satisfactory fit to the data? The argument k controls the number of knots. Try setting k to 20, and examine the fit. How might an “optimal” value of k be selected?