I import 40000 XY datapoints in ArcMap. There is another third field with 40000 different values. I would like to classify all these values in just 5-10 classes but this option doesn’t appear when I open the symbolology. Any idea?

  • In the Symbology tab, is "Show: Categories" greyed out, missing, or what? – Erica Jul 15 '14 at 15:07
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    Try exporting your points to a shapefile. It sounds like you are using them from a CSV or TXT file and I don't believe you have all of the options available for symbology when you do this. You should get more options when you convert to a shapefile or geodatabase format. – Sara Barnes Jul 15 '14 at 15:14
  • No it is not greyed out but the unique values do not appear. I have imported it from an access database. – dimitris Jul 15 '14 at 15:15
  • You have to hit the "Add all values" button to see them. – Wes Jul 15 '14 at 15:16
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    Or add specific values if you wish. Also, you may have to export to a shapefile or feature class as Sara said. – Wes Jul 15 '14 at 15:18

As @SaraBarnes said in the comments, you will likely first have to export the file to a shapefile or feature class. Next, in order to classify unique values, you have to "Add All Values" or add specific values you'd like to classify with the "Add Values..." buttons in the Symbology tab, as shown below.

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You can then set symbology based on those values.

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