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In Modelbuilder I have set up a model, where in one step I do a "Calculate Field" like "round((!OID!-1- %MyField% /15)/452,1)+1" . For the calculation i use the value of %MyField%, which actually is an Value of a specific Field in the first Row of a Table. I tried to retrieve is with "Get Field Value" - this works. But how do I ensure, that I have the value retrievet at the moment when I want to "Calculate Field"? Of cource I make an "Precondition" connection, but if "MyField" is 0 (Zero), the precondition says False, so the Calculate Field is not executed. To explain more: I iterate through features (A) in feature class. In the iteration model i create an fishnet (new feature class (B)) inside the feature. Then i add a field to the new feature class (B).Now i need to calculate this field using the formula mentioned above. In the formula i need to use a value from a field of the feature (A). Is there a way? (I use Arcgis 10.2)

  • Field calculations can only work on a single row in a table - they do not have access to data in other rows. In order to use a field calculation your constant must be present in every row, or hard-coded into the formula. – Chris W Nov 18 '14 at 20:00
  • Would you be able to edit your question to include a picture of the relevant part of your model, please? Also, include the version of ArcGIS for Desktop that you are using because ModelBuilder has had quite a few changes between 9.3 and now. – PolyGeo Nov 21 '14 at 7:00
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Finally I solved this problem. I have to use a short python-script:

import arcpy
myFeature = arcpy.GetParameterAsText(0)
myrows = arcpy.SearchCursor(myFeature)
myrow = myrows.next()
MyField = myrow.getValue("Offset_Y")
arcpy.SetParameter(1, MyField)
arcpy.SetParameter(2, True)

Where Parameter 0 as Input is the feature where the field "Offset_Y" is. Parameter 1 as Output is the value I want in the Variable, Parameter 2 as Output is Boolean and connected to Calculate Field Value.

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