I have a large shapefile of GPS points. Each point has a unique point ID number, but they are all part of different clusters, where each cluster has a unique cluster ID number (there is no overlap between clusters). For example, points 1, 2, and 3 are part of Cluster 100 and points 4, 5, and 6 are part of Cluster 200. I have done a Select by Location query of these points based on their proximity to a road feature class, and now have about 1400 points selected. I would now like to select any additional points that share a common Cluster ID to the already selected points. For example, say I captured points 1 and 2 of Cluster 100 with the locational selection query, how would I capture point 3 of Cluster 100 as well, in an efficient query? Or is there a way to have a subquery in the Select by Location query that would look at the cluster ID attribute?

2 Answers 2


Sounds like you can use the 'Select by Attributes' tool with the selection method set to 'Add to Current Selection'

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Then just build your query to select all the points with a Cluster ID for the group that you're interested in. That will add any that got missed by the spatial query.

  • Is there a query that can efficiently identify 100+ unique cluster IDs?
    – oatmeal
    Jan 5, 2017 at 22:36
  • I'm afraid I don't understand your question. If you just want to see all the unique values present in a field just select the field in the dialog box and click the "Get Unique Values" button. If you need to do things automatically - as in get the computer to do this for you - then you're looking at using a python script or maybe a model. That is a whole other ball of wax.
    – Kevin
    Jan 6, 2017 at 16:37

Here's what I ended up doing: After doing my Select by Location query, I made a selectional layer of those points within the defined proximity of the road. I then ran a Frequency tool with the Cluster ID as the only frequency field and saved the table. I then joined this frequency table to the full set of points based on the Cluster ID, keeping only matching records. I then started an editing session and deleted all the points indicated in the joined table.

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