I created voronoi polygons after which I dissolved them on the basis of one attribute. Now there are cases where in for one single attribute "abc" I have3 polygons at different places with same object id. I would like to break these into 3 polygons as they are at different locations.

Is there any tool in ArcGIS Desktop or QGIS which can help me in doing that?


I think that what you actually want to do is to convert multipart polygons into singlepart polygons.

In ArcGIS it can be done using Multipart To Singlepart (Data Management) tool.

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In QGIS vector menu, as well as in the Processing Toolbox, you'll find Multipart To Singlepart.

This algorithm takes a vector layer with multipart geometries and generates a new one in which all geometries contain a single part. Features with multipart geometries are divided in as many different features as parts the geometry contain, and the same attributes are used for each of them.

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You should specify option SINGLE_PART when running ArcGIS Dissolve tool:

SINGLE_PART —Specifies multipart features are not allowed. Instead of creating multipart features, individual features will be created for each part.

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  • As Alex said, there is an option/check box in Arcgis 9.3 Dissolve tool, - "Create multipart features", it is "checked" as default. – vadivelan Jun 20 '12 at 15:29
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    This is the best answer for preventing the problem when using ArcGIS. The Multipart To Singlepart tool (referenced by Marcin) is the best way to fix the issue after-the-fact. – user3461 Jun 21 '12 at 11:54

Another Less elegant option is to click the Explode button in Advanced Editing toolbar in Arcgis after selecting all features in Layer.

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A suggestion for all you R enthusiasts or new learners (like myself) out there: The same thing can be achieved in R with the disaggregate function from the sp library.

output <- disaggregate(input)

Simple as that.

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