Normalizing values in single Field (from table) in ArcGIS for Desktop?

Question

have encountered a problem, in Field Calculator.

The situation : I have a polygon feature with a table, comprised of a single Field ("Field1"). There are 675 records in this field. The minimum value is 0.24, and the maximum value is 2546.

What I want to do: Add a new field ("Field2"), in which I want to generate the normalized values in "Field1". By normalization, I am referring to re-scaling all the values, from 0 to 1.

What functions / expression can I use in Field Calculator, to obtain these normalized values?

Answer 1

Using Python would open up some more elegant solutions, but you can do this entirely in ModelBuilder with the use of a couple of temporary tables. The model would look something like this (note that you can right-click on any process step and rename it):

1. The Add Field operation adds a new column called [Normalized_Value] to your existing polygon table.
2. A pair of Sort operations create two new tables, one with your [Field1] sorted in ascending order, and the other sorted in descending order.
3. A pair of Get Field Value operations get the first row (the minimum and maximum values) of [Field1] and assign them to %Min_Value% and %Max_Value%, respectively. The values are available for use automatically as soon as these steps have run.
4. The min and max values are then used in the Calculate Field operation to calculate [Normalized_Value]: (([Field1] - %Min_Value%) / (%Max_Value% - %Min_Value%))
5. (Optional) You may wish to add steps to delete the temporary tables.

Answer 2

You could use the Python parser in the Field Calculator and construct this function.

This part goes in the pre-logic. Make sure to replace the feature classes with the one from your system. The feature class table called "Temp_Table" is a temporary table and must reside in a geodatabase. It will be deleted as the script completes.

def normNum(num):
  arcpy.Statistics_analysis(r'C:\Geodatabase.gdb\Original_Features',r'C:\Geodatabase.gdb\Temp_Table', [["Field1","MIN"],["Field1","MAX"]])
  with arcpy.da.SearchCursor(r'C:\Geodatabase.gdb\Temp_Table', ("MAX_Field1" , "MIN_Field1")) as cursor:
    for row in cursor:
      maxNum = row[0]
      minNum = row[1]
  del cursor
  del row
  arcpy.Delete_management(r'C:\Geodatabase.gdb\Temp_Table')
  return ((num - minNum) / ( maxNum - minNum))

This part goes in the "Field2 =" box:

normNum(!Field1!)

Here is a version that would run as stand alone function so you wouldn't need the field calculator:

def NormalizedNumbersToField(table, field, scratchGDB):
    arcpy.AddField_management(table, "NORMALIZED", "DOUBLE")
    scratchTable = os.path.join(scratchGDB, "Temp_Feat")
    arcpy.Statistics_analysis(table,scratchTable, [[str(field),"MIN"],[str(field),"MAX"]])
    with arcpy.da.SearchCursor(scratchTable, ("MAX_" + str(field) , "MIN_" + str(field))) as cursor:
        for row in cursor:
            maxNum = row[0]
            minNum = row[1]
    del cursor, row
    arcpy.Delete_management(scratchTable)
    with arcpy.da.UpdateCursor(table, ( field , "NORMALIZED" )) as cursor:
        for row in cursor:
            number = row[0]
            row[1] = (( number - minNum ) / ( maxNum - minNum ))
            cursor.updateRow(row)
    del cursor, row

Answer 3

You could do something like this...

[Field2] = (( [Field1] - 0.24 ) / ( 2546 - 0.24 ))

Basically you have to find the difference between the [Field1] value and the minimum value and then divide it by the entire range of data.

normalized = (value - minimum) / (maximum - minimum)