Proportional area symbols with graduated colors
I have a point feature set with both positive and negative data values that I want to symbolize as proportional area circles. I would like the circle area to be proportional to the absolute value of the data value. For example, -100 and +100 would have the same size circle. I would also like to use a divergent color scheme for the data so that positive and negative values have different hues. Again, by way of example, -100 would be red and +100 would be blue.
I can't figure out any obvious way to do this. I can't use the proportional classification scheme for negative data, but I could create an absolute value field and use that. That would generate all the correct sized circles. However, that scheme provides no way to generate a color ramp for the data.
I thought about creating proportional circle polygon features from the points (using buffering or something) and then symbolizing those features. However, my map is a world map and it occurred to me that polygon features would be subject to distortions found at global scales. Is that right? If so, then the circles wouldn't actually appear as the desired size (or shape, for that matter).
I also wondered whether I could do this with representations or annotation graphics, but couldn't quite figure out how to get the size color combinations I want without having to manually set each circle's attributes individually (which isn't practical in my situation).
Logically, what I want to do is symbolize the data twice, having the second symbolization not override the first. That is, symbolize the features first as proportional area circles using absolute value to set the size. Then, classify the proportional area circles using a divergent graduated color scheme based on the actual value (positive and negative). Sounds simple in concept, but not so much in practice as far as I can see.
Any ideas or guidance will be greatly appreciated. Thanks in advance.
Mapping Center Answer:
We've received this question before so check out the following answer for a way to do this currently:
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