Hey Nitin!
The rankings are from the relative sorted positions (lowest to highest) of each element's pymatgen mendeleev number.
For example, if you only have 3 elements in a dimension, with mendeleev numbers [50, 1, 22] your ranked mendeleev numbers would be:
[3, 1, 2]
In two of our dimensions, we had 52 elements,. so the mendeleev ranks were from 1-52.
For polyatomic anions, we took the average (weighted by stoichiometric proportion of each element) of the mendeleev numbers for the constituent elements. Then we ranked each anion's average mendeleev number (lowest to highest) in the same way as above.
In our experiment the third dimension was 7 different anions. So they were ranked between 1-7. So for example, the ABX ranked mendeleev vector [1, 52, 3] represents
[the lowest mendeleev number element, the highest mendeleev number element, the 3rd highest weighted average mendeleev number anion]
Thanks,
Alex