</h3>
<p>Finding a common tiling of several different yet congruent geographies is only one part of the problem TongFen addresses, aggregating up the variables is the other part. The <code>tongfen</code> package deals with this using a <em>metadata</em> table that specifies how variables should be aggregated. In it’s simplest form values are simply added up. The <code>meta_for_additive_variables</code> convenience function builds the metadata for additive variables. Metadata for non-additive variables lik