Here is a puzzle that I've worked at for a while with out much result. Take profile station-elevation data, in this case stream profile data cut from a less than perfect LiDAR source, and filter the data such that only local minimum ordinances are left resulting in a station-elevation series that "drapes" on the minimum values. See the example attached. In this case the original data is plotted in blue, and I want to filter the data to result in something that resembles the red line. Any thoughts?