For my applications, using natural cubic splines provided by the 'ns' function in R, combined with trying out where knots should be positioned, is sufficient. M

For my applications, using natural cubic splines provided by the 'ns' function in R, combined with trying out where knots should be positioned, is sufficient. Maybe have a look at the gratia package [1] for plotting lots of diagnostics around spline fits. [1] https://cran.r-project.org/web/packages/gratia/vignettes/gratia.html https://cran.r-project.org/web/packages/gratia/vignettes/gra...