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Comment by vilhelm_s | Hacker News Reader

I was thinking the same thing. According to Wikipedia, the county areas vary by three orders of magnitude, from San Bernardino County, California (51,947 km^2) to Kalawao County, Hawaii (31 km^2), so it seems it can be very misleading.

For example, North Carolina and California have similiar population densities (80 people/km^2 versus 95 people/km^2), but on the "muddy" map North Carolina looks almost unpopulated while California is very emphasised---I guess this is because North Carolina is divided into smaller counties.

I guess in the case of San Bernardino it's a giant grey rectangle, so that particular one doesn't shift the red-blue impression very much, but still... :)

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something like votes per square mile may address this. Looks like there are some follow-up maps to be made =)

I agree - this was my one minor nit-pick after reading the post as well.

I'd love to see muddy maps for other past presidential elections if you can get a hold of the data (and this one too, once all the votes have been counted).

Really cool work, and well-explained!

I experimented a bit with the source code at https://github.com/tuttlepower/VotingMap , you can add an area correction by changing the line

    fillOpacity: (us_votes[i].total_votes / 59828),

to something like

    fillOpacity: (us_votes[i].total_votes / (59828 * 50 * (feature.properties.AREALAND / 5.195e10))),

But I think in practice, this effect is swamped by the "upper fence" effect described in the original post. In other words, the scale is very far from linear anyway, by changing the magic number 59828 above you can make it look dramatically different. I should really calculate what the (Q3 + 1.5 * IQR) value is, but above I just put in a "* 50" to make the overall impression of the map similar.

The resulting image: https://imgur.com/3K8Wwan

yep the upper fence for the vertical scale is derived from the vote totals statistics. If the set of vote totals is now in votes per square mile, then there would likely be a different upper fence. Might be worth the number crunching to figure out what that number is.

BTW just to double-check, I'm assuming that in this given fillOpacity formula, that a fillOpacity > 1 just resolves to 1. So like fillOpacity : min(votesPerSquareMile/upperFence, 1).

Yeah, the Esri fillOpacity property just becomes an SVG property, and the SVG specification requires that it gets clamped to [0,1] before rendering.

In addition to computing the quartiles correctly, I also realized you should probably use (AREALAND+AREAWATER) rather than just AREALAND... in the above image the great lakes counties look suspiciously overemphasized. :)

let me know how it turns out! Do you have a link to your fork?

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