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compound/complex symbol for pointdata

May 29 2009 | 2 comments
Categories: ArcGIS Methods, Map Data

I have a dataset from which I would like to represent data from multiple colums in a single symbol which looks like a pie chart. The symbol would have to be divided in the same amount of sections as there are columns of data. The color of each section would be determined by the value in the corresponding column.

The number of variables within a layer can differ (up to 10) as can the number of states to be presented (up to 5).

For example:
I have data for the water quality at a sample site. Four variables are measured. The required symbol would therefore be divided in four sections. Each section represents one variable. If the data is below threshhold_1 the color for the section of the symbol should be green. If the value is between threshhold_1 and _2 it should be yellow and when it is above threshhold_2 it should be red. If no data is available it should be blank or transparent (only outline of the section visible).

Is it possible to create such a symbol and if so how (preferably using Arcmap 9.3)

Mapping Center Answer:

That's an interesting idea--and of course the pie chart symbols don't do that. 

What you would need, instead, is attributed pie wedge geometry.  I'm thinking you could make some "dummy" data that would give you equally sized pie chart wedges in the number of wedges you require.  Convert those to graphics, and then convert those graphics to features.  Then use the Identity tool to assign the values to the wedges from your original data. That latter part will be tricky since you'd need to select only all the 10:00 to 2:00 wedges, and run Identity, then do the same for the 2:00 to 6:00 wedges.  A trick to do that is to create centroids for your polygons and then select them all, moving them such that they overlap the correct wedge in each pie.  Then create another set of offset centroids for each of the wedges.



graphics converted to point features posted by Erik Sietinga on Jun 10 2009 5:35AM
My original data is a point feature class. As you suggested I added 5 dummy columns to create the desired number of wedges in the pie chart symbology and converted these to graphics.

However, when I convert these graphics to features using this method:
Converting features into graphics
1. Right-click the layer in the table of contents that you want to convert to graphics and click Convert Features To Graphics.
2. Click All to convert all features or click Selected to convert the selected features.
3. Choose whether you want to draw only the graphics or both the features and the graphics after the conversion.
4. Set the target where you want to store the graphics. The default target saves the graphics to your map document.
5. Click OK.

This gives me a point shapefile instead of the expected polygons with the individual wedges. Basically I'm back to square one. I checked in the graphics toolbar if I could ungroup or explode the graphics but no such option is available.

Any pointers on how to get the individual wedges?

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