Get data from column of horizon or site data in a SoilProfileCollection
Source:R/SoilProfileCollection-operators.R
dollarsign.RdGet the data from a column accessed by name x$name. Column
names other than profile ID are not shared between site and horizons.
Accessing the profile ID column (idname(x)) with $ returns the
horizon-level data with profile ID repeated for each horizon in a profile.