Request for advice on downscaling

Hello Everyone,

Please pardon my ignorance, but as I am new to spatial analysis,
I am writing for some guidance to approach a particular spatial analysis
problem
and would really appreciate it if I could get some advice in that regard.

I have a large shapefile and within that shapefile, it is subdivided into
several grids. I have the population data for each of the subgrids and I
would like to partition (or downscale) one large number across the subgrids
, weighted by population.

Can anyone suggest some useful approach or particular R package that
can help me address the problem.

Thanks for your time,

Sincerely,
Bhaskar Mitra