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I have a bunch of polygons (counties) that I need to merge together. They all have various population attributes. I need to be able to selectively merge two counties together and get a single polygon with the combined population totals for the attributes. Is there a way to do this in ArcGIS?

I've tried the Merge tool but while that works for the boundaries, it doesn't work for the adding the two population totals together, you have to pick one or the other. The Dissolve tool seems to operate on all polygons with a single attribute, but there is no unifying attribute that I have that determines which polygons are merged.

Thanks.

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    Have you tried selecting the counties either manually or by SQL prior to doing the dissolve or merge? – Aaron Jul 9 '13 at 1:37
  • Not posting an answer, because you asked for a arcgis solution, but QGIS has a merge tool while in editing mode that can merge the selected features gemometries and asked what you want to do with each attribute fields. One of the options is to sum the values. – Alexandre Neto Jul 9 '13 at 10:30
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As Aaron alluded to in his comment, if any features of a layer are selected prior to using that layer as an input to a geoprocessing tool, the input is restricted to the selection.

In your particular case, you should be able to select two (or more) countries with the Select tool or Select By Attributes/Location dialogs and then run the Dissolve tool, selecting the feature layer (not the path to the actual shapefile/feature class itself) by its name from the input features dropdown menu.

The Dissolve tool has an optional parameter, statistics_fields, where you can SUM the population.

  • The Dissolve tool has an optional parameter, statistics_fields, where you can SUM the population. – klewis Jul 9 '13 at 14:02
  • @klewis exactly. I assumed he knew that, as his problem with the Dissolve tool was that he could only get it working on all polygons in a feature class simultaneously. – nmpeterson Jul 9 '13 at 14:07
  • Ok this works. However it is a lot of work to set up the optional parameters to SUM over 50 different fields every single time. Is there a way to automate the SUMing of all the fields? I have to run the Dissolve tool over 500 times and would really prefer not to have to set up the SUMming of 50 different fields each time. – Josh Jul 18 '13 at 15:46
  • Nevermind. I used Model Builder to fix this problem. Thanks guys. – Josh Jul 18 '13 at 16:48

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