Using conditional statements in ArcGIS Field Calculator?

Question

I have two fields, "P_Area" and "PC_Area", whose sizes I'd like to compare in a third field, "Areas_Equal". The "Areas_Equal" field should contain a "Yes" if the other two are equal and a "No" if they aren't.

How can I do this with Field Calculator and its Python Parser?

Stev_k · Accepted Answer · 2012-03-19T11:52:41.103

7

If you're using Python in ArcGIS you may be using an = for comparison instead of an ==

Your code should be similar to the below, if you use Python:

Pre-Logic Script Code - Check "Show Codeblock"

def ifBlock(pArea,pcArea):
  if pArea == pcArea:
    return 1
  else:
    return 0

Then in the actual code:

ifBlock(!P_AreaFieldName!,!PC_AreaFieldName!)

edited Mar 19 '12 at 11:52

answered Mar 19 '12 at 09:54

Stev_k

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6

And, of course, if he wants "Yes" and "No" instead of 1 and 0, he should use return "Yes" and return "No". – nmpeterson Mar 19 '12 at 13:44
1

Another way to write this in Python (that doesn't require the code block) is this... 1 if !P_Area! == !PC_Area! else 0 – Jason Miller Aug 12 '14 at 02:35

score 2 · Answer 2 · edited Mar 19 '12 at 12:40

Please always mention which tool you are using. I will explain how to do this in QGIS because it's free.

Open your shapefile. Open the attributes table. At the bottom create a new columon, call it 'test' or whatever. Now click on advanced search. Type 'P_Area = PC_Area' (without quotes) in SQL where clause. Hit OK.

Now click on 'Open field calculator' (ctrl+I). On the top check 'update existing field' and 'only update selected features'. In field calculator, type '1'. Hit ok.

Now, go back to advanced search, this time search for 'P_Area != PC_Area'. Do same steps as above, except input '0' in field calculator instead of '1'.

I am sure you can do it in a smarter way, but hey, this works. :)

Using conditional statements in ArcGIS Field Calculator?

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