FAQ: Can I Select Features at Random?

Answer

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The following ArcObjects sample code illustrates how to select random features. Specify the number of features to select on the line that is marked.

Code:
Sub SelectRandom() 
Dim pMxDoc As IMxDocument 
Dim pFeatureLayer As IFeatureLayer 
Dim pFeatureCursor As IFeatureCursor 
Dim pFeature As IFeature 
Dim pFeatures() As IFeature 
Dim pFeatureSelection As IFeatureSelection 
Dim lTotNumFeatures As Long 
Dim lNumFeatures As Long 
Dim lFeatureCount As Long 
Dim lRandom As Long 
Dim dPercentage As Double 
Dim l As Long 

'set number of features to select
lNumFeatures = 500

Set pMxDoc = ThisDocument 
Set pFeatureLayer = pMxDoc.FocusMap.Layer(0) 
 
lTotNumFeatures = pFeatureLayer.FeatureClass.FeatureCount(Nothing)  

ReDim pFeatures(0 To lTotNumFeatures - 1) 
Set pFeatureCursor = pFeatureLayer.FeatureClass.Search(Nothing, False) 
Set pFeature = pFeatureCursor.NextFeature 
Do While Not pFeature Is Nothing 
Set pFeatures(l) = pFeature 
l = l + 1 

Set pFeature = pFeatureCursor.NextFeature 
Loop 
 
pMxDoc.FocusMap.ClearSelection 

l = 0 
Do While l < lNumFeatures 
lRandom = CLng(Rnd * (lTotNumFeatures - 1)) 
If Not pFeatures(lRandom) Is Nothing Then 
 
pMxDoc.FocusMap.SelectFeature pFeatureLayer, pFeatures(lRandom) 
 
Set pFeatures(lRandom) = Nothing 
 
l = l + 1 
End If 
Loop 

'Refresh 
pMxDoc.ActiveView.Refresh 
End Sub

Article ID:000007142

Software:

ArcMap 8 x

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Can I select features at random?

Answer

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