[GIS] Filling in new field in attribute table based on values of another field in ArcGIS Desktop

arcgis-desktopattribute-table

I have added a new field (Category) in an attribute table of a shapefile and I would like to fill it with numbers, 0 or 1, based on the numbers of another field (Calorific value) of the same attribute table.

That means that if the Calorific value is higher than 15, then I would like to fill in the corresponding cells of the (new) Category field with 1. If the Calorific value is less than 15, then the rest cells of the (new) Category field to be filled in with the number 0.

Is there a way to do this automatically rather than manually?

Best Answer

You can do this automatically using Field Calculator with a code block.

def classify(field):
    if (field > 15):
        return 1
    elif (field <= 15):
        return 0

classify( !CalorificValue!)

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ArcGIS Desktop – Computing New Attribute Based on Changes in Another Attribute Using Python

For this you can use UpdateCursor, which opens the feature class or table and steps through each record (row) incrementally.

The script below works on this test data

+-----------------------+
| Time| Home_Away|Trip  |
+-----|----------|------+
|  1  |  0       | <nul>|
|  2  |  1       | <nul>|
|  4  |  1       | <nul>|
|  5  |  0       | <nul>|
|  6  |  0       | <nul>|
|  7  |  1       | <nul>|
|  9  |  1       | <nul>|
| 12  |  1       | <nul>|
| 13  |  0       | <nul>|
+-----------------------+

import arcpy
fc = r'D:\s\py\pyscratch.gdb\gps_points'

# open the feature class and create the cursor
rows = arcpy.UpdateCursor(fc)

trip = 0
for row in rows:
    if row.HOME_AWAY == 0:
        trip += 1           # start of new trip, increment counter
        row.TRIP = trip     # calc the TRIP field to be current trip#
        rows.updateRow(row) # save
        print "Trip %s started at %s" % (trip, row.TIME)

    # keep cycling through records until HOME_AWAY is not 1
    while row.HOME_AWAY == 1:
        row.TRIP = trip
        rows.updateRow(row)
        rows.next() # move to next record

    # this is for the trailing end of a trip, the second 0
    # print "     %s ended at %s" % (trip, row.TIME)
    row.TRIP = trip
    rows.updateRow(row)

# remove programming objects and data locks
# the data itself is left alone
del row, rows

The trailing end of trip block is actually run for the beginning of a trip also, but since the trip counter is correct the double calc on the begin-trip-row doesn't matter . Uncomment the print statement in that block to see what I mean.

Python automatically adds an implicit rows.next() at the end for the for row in rows block.

This assumes data integrity. It will mess up if there are ever an odd number of zero Home/Away records in a row (000 or 00000). A trip that only consists of start and stop should be okay, e.g. a 3 trip sequence of 01..10 00 01..10 , where the spaces denote the gaps between trips. In other words, validate the results!

[GIS] Generating Values in Attribute Table using ArcGIS Desktop

Well, if you've got a table that natively (sorted by FID or ObjectID as applicable) is NOT sorted how you want it, and you want to view the table sorted by a specific field(s) with a unique ID field in order of the sort, you don't need to mess with any scripting at all.

Just use the SORT geoprocessing tool that is included in ArcGIS (In ArcToolbox > Data Management Tools > General > Sort ). This tool should do what you're asking for because there will be a new OID/FID for the resulting dataset that is in order with the sorted values.

More info on the Sort GP tool is available at http://resources.arcgis.com/en/help/main/10.1/index.html#/Sort/001700000057000000/

Best Answer

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