Delete identical by size?

Question

I got a Feature class with some identicial fields! Now i only need one polygon which had the same ID and this is the one with the largest size? Is there a posibility to delete the Polygons which are identical by size so that only the largest Polygons(from the ones with the same ID) are left?

For example:

ID   shape area

1    5
2    4
2    3
3    11
4    7
5    8
5    10

and i Need only the Polygons with the largest size that means the frist, second, fourth, fifth and the last!

Answer 1

I would run the dissolve tool.

1. Open Toolbox
2. Data Management Tools/Generalization/Dissolve
3. Choose your file as the input
4. Dissolve on the relavent fields (not sure what all your data looks like so I can't give a good recommendation here)
5. In the statistics portion select the ID field and then Statistic Type: MAX

Run the tool and you should get the results you are looking for.

Answer 2

This script (python) will check the records in your layer and add the IDs and their sizes to a dictionary and end with each ID associated with the largest value, then select and delete anything that is not in that dictionary.

import arcpy
dict_IDs ={}
layer = arcpy.SearchCursor("YourLayer")

for i in layer:
    record= i.getValue('Id')
    if record in dict_IDs:
        if dict_IDs[record]<i.getValue('size'):
            dict_IDs[record]=i.getValue('size')
    else:
        dict_IDs[record]=i.getValue('size')

for record_id in dict_IDs:
    qry="Id= "+str(record_id)+" and size <> "+str(dict_IDs[record_id])
    arcpy.SelectLayerByAttribute_management("YourLayer","ADD_TO_SELECTION",qry)

arcpy.DeleteRows_management("YourLayer")

Answer 3

Unless I have misunderstood what you are asking, a single tool can do this, it is the Delete Identical tool. The only caveat is that it requires Advance (ArcInfo) license level.