I know this is cheating and missing the point, but using d3-array: d3.mean(victorianSlang, d => d.popularity) This implicitly ignores invalid values (null, Na

I know this is cheating and missing the point, but using d3-array: d3.mean(victorianSlang, d => d.popularity) This implicitly ignores invalid values (null, NaN or undefined) after coercing to a number.