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I have a point data with multiple categorical values for each point location. For example:

point1 = a,b

point2 = a

point3 = b,c

point4 = a,b,c,d,e

and so on

Note that the values are categorical/nominal, therefore, I cannot create some form of ranking among data points. What map visualization options can I do with this type of data?

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a good answer would probably depend on how many categories you are working with. Are there only 5 possible categories or did you mean this as a general question of how to visualize the assignment of multiple categories to points? –  BenjaminGolder Mar 31 '11 at 8:55
@BenjaminGolder, this is both a general and my current situation. I have many categorical data sometimes more than 5 categories. In most cases a single point can have 3-4 categorical values. I'm trying to normalize the data. –  maning Mar 31 '11 at 8:58
I'm not sure what you mean by "normalize the data" in this case. –  BenjaminGolder Mar 31 '11 at 9:45
Since the values are nominal why not just map each as its own separate point pattern? –  Andy W Mar 31 '11 at 12:14
@maning , if you want to maintain the markers on the same map you can "jitter" the point markers. While the other answers so far are fine, they only make sense if you want to view the proportion of some attribute at a specific place. If you just want to see the spatial distribution of each item, I don't think they will be very effective. –  Andy W Mar 31 '11 at 13:34
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2 Answers

up vote 9 down vote accepted

I think the answer depends a lot on the conceptual differences between the categories, and whether or not having all categories implies a sort of wholeness. With large numbers of categories, it gets really tricky.

Try giving a more specific example. The meaning of the data might lead to a good solution.

In any case here are some quick sketches for point markers. The "pie chart" one would probably be easiest with existing tools.

some possible point markers

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this answer to another thread might has some neat ideas: gis.stackexchange.com/questions/4568/… –  BenjaminGolder Apr 1 '11 at 1:34
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I have BenjaminGolder similar vision : a color code is probably appropriate. But the feasibility depends of the density of your points. For my part, I would propose something like that : category and points

with of course a nice legend ;-))

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your proposal is very nice as well but I selected BenjaminGolder's answer for this case. Now the challenge would be what existing tools can do this. :) –  maning Mar 31 '11 at 10:36
Thanks. As Benjamin says, the pie chart is probably the easiest way of representing your data. It could be done, I guess, with almost GIS software, with quantitative extra columns. –  simo Mar 31 '11 at 10:43
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