topic Re: populate a field in a raster dataset based on the total SUM of another field in Python Questions

populate a field in a raster dataset based on the total SUM of another field

ThilinaSurasinghe — Wed, 04 May 2011 00:25:55 GMT

I have multiple land-use land-cover raster layers, of which the attribute tables have a field on the total area coverage by different land-use type (field name is AREA). My goal is to have another column populated with the percentage area coverage for the each land-use land cover type in the rate dataset.
I tried to do this by populating another column in the same attribute table with the summation (total summation, not cumulative summation) of AREA. If I could get this column, I can write a simple expression in the "calculate field tool" to calculate the percentage coverage.
I have nearly 100 raster layers with different geometric shapes so that I need to do this via model builder. Since this is an iterative process, calculating the column sum by the "calculate statistics tool" in not useful either.
Does anyone have a tool or a python script for this? I am using ArcGIS 10.
Thanks.
Thilina

Re: populate a field in a raster dataset based on the total SUM of another field

JakeSkinner — Sat, 11 Dec 2021 16:44:19 GMT

Here is an example on how you can sum the Area field into a new field (SUM_Area). From there you can calculate the percentage.

list = []

lstRasters = arcpy.ListRasters("*")
for raster in lstRasters:
    rows = arcpy.SearchCursor(raster)
    for row in rows:
        list.append(row.Area)
    S = sum(list)
    arcpy.CalculateField_management(raster, "SUM_Area", S)
    list = []

del row, rows

Re: populate a field in a raster dataset based on the total SUM of another field

KhanKamruzzaman — Mon, 04 Jul 2011 23:51:13 GMT

Hi JSkinn3,
I have a similar kind of question like tdilan1980 . I want summarise a field of my table and update the output into another field.
I know how to do in python window but don�??t know how to do it in �??Filed Calculator window in ArcMap table.
Specially, how do you write a code for "arcpy.SearchCursor" function in their?

Any help would be highly appreciable?

Re: populate a field in a raster dataset based on the total SUM of another field

JakeSkinner — Sat, 11 Dec 2021 16:44:22 GMT

Below is an example on how you can do this using the Field Calculator. Be sure to check 'Python' at the top and 'Show Codeblock'. Under 'Pre-logic Script Code' enter the following:

def update():
  import arcpy
  list = []
  rows = arcpy.SearchCursor(r"C:\data\Parcels")
  for row in rows:
    list.append(row.AREA)
  S = sum(list)
  del row, rows
  rows = arcpy.UpdateCursor(r"C:\data\Parcels")
  for row in rows:
    row.AREA2 = S
    val = row.AREA2
  del row, rows
  return val

Then, under the second block enter:

update()

Re: populate a field in a raster dataset based on the total SUM of another field

KhanKamruzzaman — Mon, 18 Jul 2011 08:26:43 GMT

Hi JSkinn3
Excellent!!. It works perfectly. Thanks a lot.