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> Turns even the largest data into images, accurately The first image, the image of the USA, seems really mis-representative to me. LA and NYC should be way wa
by tokyodude 8y ago
> Turns even the largest data into images, accurately
The first image, the image of the USA, seems really mis-representative to me. LA and NYC should be way way way more bright in relation to everything else than the entire area east of the Mississippi.
At least to my eyes that map makes it look like parts of Denver, Kansas City, Salt Lake City, Atlanta, and the San Joaquin Valley are just as dense as Manhattan.
Atlanta's population density 630 per square mile
Manhattan's population density 70826 per square mile
It seems like an accurate data image would have Atlanta's brightness 1/100th of Manhattan's. Basically it looks like they saturated out at around 250 people do anything over 250 people is the same brightness.
- jbednar 8y agoBy default, Datashader accurately conveys the shape of the distribution in a way that the human visual system can process. If you want a linear representation, you can do that easily; see the first plot in http://datashader.org/topics/census.html http://datashader.org/topics/census.html , but you'll quickly see that the resulting plot completely fails to show that there are any patterns anywhere besides the top few population hotspots, which is highly unrepresentative of the actual patterns in this data. There is no saturation here; what it's doing in the homepage image is basically a rank-order encoding, where the top brightness value is indeed shared by several high-population pixes, the next brightness value is shared by the next batch of populations, etc. Given only 256 possible values, there has to be some grouping, but it's not saturating.
- pwang 8y agoYes, datashader actually gives you the ability to dial-in as much gamma compensation as you want, to account for the human visual system's nonlinear response to luminance.