This should be fairly easy in theory, but would require a fairly taxing input file from the user. Right now, all of the number fractions are static scalars input by the user when they add species. We'd need to require "number fraction profiles" and we'd have to be careful to ensure that those inputs are self consistent with the mass density profile. However, if we required number DENSITY profiles, we could remove the need to input the mass density profile separately. You'd want to calculate and store it on initialization though to save some computational costs.
This should be fairly easy in theory, but would require a fairly taxing input file from the user. Right now, all of the number fractions are static scalars input by the user when they add species. We'd need to require "number fraction profiles" and we'd have to be careful to ensure that those inputs are self consistent with the mass density profile. However, if we required number DENSITY profiles, we could remove the need to input the mass density profile separately. You'd want to calculate and store it on initialization though to save some computational costs.