Data visualization: a better way to understand statistics

Posted: June 20th, 2010

I recently came across this crime-city-light-map of San Francisco. The lights you see above, are not the lights of San Francisco. Each light represents crime data. The more and ¬†brighter the lights are, the more crime there is. For once, good is represented by darkness, and light is represented by evil. I think it’s actually a very deceiving map due to the way the data is visualized. Since the good is represented by darkness, there ends up being a lot of black on the map. But, we typically associate good with light and dark with evil. So, it’s playing a trick on our minds. When I first saw this map, I thought wow! There is a lot more crime in San Francisco than I realized. Looks like a pretty dangerous place.

But if you switch it. If you make the crime black and the good light (white) then it doesn’t feel so bad. Feels fairly safe. The impression you get from the map below is completely different even though it’s showing the same data, just in a different way. Now we see lots of white (good) and just a touch of bad (black and blue) throughout the map. I’d definitely rather live in the city below rather than the one above.

I also found some crime-elevation-maps that I thought were really cool (see below). The mountains you see are not the actual mountains and hills of the city. They’re hills that represent the amount of crime in the city. These were created by¬†Doug McCune, check out his blog post. He also created the first dark city light map you see above. I created the second one by inverting his image.

These maps are great, because they take data that would be incomprehensible to most of us, and become instantly understandable. A quick glance at these maps and you can easily tell what areas of the city have the most crime and which areas don’t. I’d be interested in inverting these maps too (I lack the technical skill to do so). What would they look like if the crime areas were represented by giant craters/holes in the city? Would they give you a different impression of the city?

The San Francisco Chronicle also wrote a short article on these maps.

San Francisco Crime Map by Elevation



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