Need functionality to scale the density over an entire layer and set Z/A values for each step

In trying to bin the Earth into equal sized depth bins over which to scale the electron number density, I ran into problems with the bin edges not lining up with the constant Z/A layers. To solve this problem, I intend to add a function that allows me to set Z/A values for each density step, instead of the indexed layers, so I can use the indices to define the depth bin that needs scaling. I also intend to add a function that allows me to choose an index and scale the density in every step labeled with that index.