I am trying to calculate a mean across a multiple number of attribute rows and have this value added to a new field that I have entered in the attribute table. I have an attribute table which has a number of different ecoregion types associated with them.

For example:

If I select "Arid Canyonlands" there are 3 attribute rows that are selected, each with their own "mean". I am trying to add a new field to the attribute table which will take the "mean" of these three and populate that value in the new field created. I could manually do it through an editing session and using a calculator but just wanted to know if there is an easier way to actually do it through field calculator?

  • 1
    Can you maybe post a screenshot how the table looks like?
    – ustroetz
    Oct 2, 2013 at 23:35
  • 1
    I think you should use the Summary Statistics tool to calculate the mean.
    – PolyGeo
    Oct 3, 2013 at 0:01
  • 1
    Do you mean attribute column? Because taking the mean of several rows and sticking it into the column of one feature seems that it wouldn't be valid
    – Brad Nesom
    Oct 3, 2013 at 1:33
  • When you say 'their own "mean" ', do you mean they already have a field named mean that you want to find the average of?
    – Sarah
    Oct 4, 2013 at 15:25

1 Answer 1


I think you should use the Summary Statistics tool to calculate the mean:

Calculates summary statistics for field(s) in a table.


The following statistical operations are available with this tool: Sum, Mean, Maximum, Minimum, Range, Standard Deviation, Count, First, and Last. The Median operation is not available.

Your "ecoregion type" field would be used as a case field:

If a Case field is specified, statistics will be calculated separately for each unique attribute value. The Output Table will contain only one record if no Case field is specified. If one is specified, there will be one record for each Case field value.

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