I'm stuck in a problem when I started calculating area in arcmap 10.1. In the picture, I categorize my polygon into four unique labels - i.e. vegetation, sand fill, water body, built-up area. Now I want to calculate the area of these four categories. But when I opened the attribute table and try to calculate the area of each category, there are many polygons having the same gridcode. Also I tried to add another field called Name
but can't. Can anyone please tell me how I can do this ?
1 Answer
If you already have the Name field, as your images shows, then right-click on the field header and select "Field Calculator...". In the field calculator window, enter an expression in either VB Script or Python which checks the value of GRIDCODE and returns the appropriate name for each of the four possible values.
To calculate the total area for each type of polygon, use the Summary Statistics tool (ArcToolbox > Analysis Tools > Statistics).
- The Input Table will be your existing polygon dataset ('polygon' in your example).
- Set your Output Table as desired.
- The Statistics Field will be the field which contains the area. Once you have selected the field, you will also need to enter the Statistics Type of sum in the table.
- The Case Field will be the attribute which differntiates between the polygon type (GRIDCODE in your example)
Note that when you first enter the Statistics Field, a red X will appear next the that part of the tool until you enter the statistic type into the table
-
Thank you very much. It worked ! I calculated area under each GRIDCODE successfully but I can't understand how to enter an expression in VB Script or Python as I have very poor knowledge in Python. Jun 15, 2016 at 10:21
-
I think that really could be a second question. If you post it I'm sure it'll get a quick response.– AdamJun 15, 2016 at 22:16
Name
field but I can't edit this. I thought, if i, somehow, manage to edit the field, I can calculate area of each category. @BradNesom