Use IHistogram::GetHistogram to return the values and frequency for a numeric field

Summary

Instructions provided describe how to perform Frequency commands for numeric fields in ArcMap using VBA and ArcObjects. ArcInfo has a Frequency command that returns a list of unique code occurences and their frequency for numeric and text fields.

Procedure

1. Start ArcMap.
2. Open the Visual Basic Editor.
   
   
   In ArcMap, select Tools > Macros > Visual Basic Editor.
   
   
3. In the Project Explorer window, expand Project.mxt and select ArcMap Objects > ThisDocument. Right-click and select View Code.
   
   

   Note:
   Code in the ThisDocument module will only run in the current map document. To store the code in all your map documents, open the Normal.mxt ThisDocument code module. 

   
   
4. Copy the following code into the code module.
   
   

   Code:
   Sub TestHistogram()
   Dim pDoc As IMxDocument
   Set pDoc = ThisDocument
   Dim pMap As IMap
   Set pMap = pDoc.FocusMap
   
   Dim pLayer As IFeatureLayer
   Set pLayer = pMap.Layer(0)
   Dim pTable As ITable
   Set pTable = pLayer.FeatureClass
   
   Dim pTableHistogram As ITableHistogram
   Set pTableHistogram = New TableHistogram
   
   Dim pHistogram As IHistogram
   Set pHistogram = pTableHistogram
   
   ' Get values and frequencies for STATE_FIPS
   ' for the US Counties layer into a table histogram object
   pTableHistogram.Field = "STATE_FIPS"
   Set pTableHistogram.Table = pTable
   
   Dim dataFrequency As Variant
   Dim dataValues As Variant
   pHistogram.GetHistogram dataValues, dataFrequency
   
   ' Loop through the values returned by GetHistogram
   For i = LBound(dataValues) To UBound(dataValues)
     Debug.Print dataValues(i) & " " & dataFrequency(i)
   Next i
   End Sub

   
   
5. If the Intermediate Window is not open in the Visual Basic Editor, choose View > Intermediate Window to display it.
6. Run the code.
   
   
   A. Click Tools > Macros > Macros to display the Macros dialog box.
   B. Select a macro and click Run.
   
   
7. The Intermediate Window will list the unique values found and the frequency of occurences for each value.