4 replies to this topic

[oskarlin]

I'm making a political map of the world and want to use six different nation colors. Is there a function in ArcGIS for setting colors of each country so that no adjacent countries has the same color?

Thanks in advance!

[frax]

Not sure if there is... I just looked at the ESRI data and maps data as well as Natural Earth, and both of these have a field for color codes - NE has 13 colors, while the ESRI dataset has 8. Maybe something to start from?

[natcase]

You should be able to do it with 5 colors. Just start with one color and then for each uncolored country, select the one that is used furthest away. For ease of further use, when you're done and happy with the scatter of colors, assign a value to a new field for "country color", value 1-5.

And it's not just non-adjacency but overall density: You don't want two big countries with one little country separating them to be the same color.

Nat

[Matthew Hampton]

During the Portland Cartography Symposium yesterday I came across a script that should do the trick for you.

[Charles Syrett]

That script is for 4 colours. This is the theoretical minimum number of colours that can be used to colour any map, according to the definition of "map" used by mathematical theorists (see the Wikipedia article about the 4 colour map theorem). Of course, in real-world cartography, you have to take into account oceans (usually blue), as well as other colour conventions and client-requested colours.

Oskarlin: you say you want to work with 6 colours. I'm not sure whether the Arc script could be adapted to 6 colours.....but in the meantime, why not just go through the process that Nat suggested? Having done it many times, I can verify that it's fast, enjoyable, and highly effective. No need for clunky things such as brewers or scripts.

Charles Syrett
Map Graphics
http://www.mapgraphics.com