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Add Field to Analysis Layer

Summary

Adds a field to a sublayer of a network analysis layer.

Usage

  • The tool is mostly used along with the Add Locations tool to transfer fields from the input features to the sublayers. For example, if you want to transfer a field called UniqueID from your input features into the Facilities sublayer of the Service Area layer, use this tool to first add the UniqueID field to the Facilities sublayer, and then use the field mappings in the Add Locations tool to provide input values for the UniqueID field.

  • Fields can be added to any of the sublayers of the network analysis layers.

Syntax

AddFieldToAnalysisLayer_na (in_network_analysis_layer, sub_layer, field_name, field_type, {field_precision}, {field_scale}, {field_length}, {field_alias}, {field_is_nullable})
ParameterExplanationData Type
in_network_analysis_layer

The network analysis layer to which the new field will be added.

Network Analyst Layer
sub_layer

The sublayer of the network analysis layer to which the new field will be added.

String
field_name

The name of the field that will be added to the specified sublayer of the network analysis layer.

String
field_type

The field type used in the creation of the new field.

  • LONG Whole numbers between -2,147,483,648 and 2,147,483,647.
  • TEXTAny string of characters.
  • FLOAT Fractional numbers between -3.4E38 and 1.2E38.
  • DOUBLE Fractional numbers between -2.2E308 and 1.8E308.
  • SHORT Whole numbers between -32,768 and 32,767.
  • DATEDate and/or time.
  • BLOBLong sequence of binary numbers. You need a custom loader or viewer or a third-party application to load items into a BLOB field or view the contents of a BLOB field.
String
field_precision
(Optional)

The number of digits that can be stored in the field. All digits are counted no matter what side of the decimal they are on.

The parameter value is only valid for numeric field types.

Long
field_scale
(Optional)

The number of decimal places stored in a field. This parameter is only used in float and double data field types.

Long
field_length
(Optional)

The length of the field being added. This sets the maximum number of allowable characters for each record of the field. This option is only applicable on fields of type text.

Long
field_alias
(Optional)

The alternate name given to the field name. This name is used to give more descriptive names to cryptic field names. The field alias parameter only applies to geodatabases.

String
field_is_nullable
(Optional)

Specifies whether the field can contain null values. Null values are different from zero or empty fields and are only supported for fields in a geodatabase.

  • NON_NULLABLEThe field will not allow null values.
  • NULLABLEThe field will allow null values. This is the default.
Boolean

Code sample

AddFieldToAnalysisLayer example 1 (Python window)

The following Python window script demonstrates how to add a UniqueID field to the Facilities sublayer of the Service Area network analysis layer.

arcpy.na.AddFieldToAnalysisLayer("Service Area", "Facilities", "UniqueID",
                                    "LONG")
AddFieldToAnalysisLayer example 2 (workflow)

The following stand-alone Python script demonstrates how the AddFieldToAnalysisLayer function can be used to transfer the StationID field from the input fire station features to the 2-, 3-, and 5-minute service area polygon features calculated from a service area analysis. The StationID field can be used to join other attributes from the fire station features to the service area polygon features.

# Name: AddFieldToAnalysisLayer_Workflow.py
# Description: Transfers the Address field from the input fire station
#              features to the 2-,3-, and 5-minute service area polygon features
#              calculated from a service area analysis. The Address field can
#              be used to join other attributes from the fire station features
#              to the service area polygon features.
# Requirements: Network Analyst Extension

#Import system modules
import arcpy
from arcpy import env
import os

try:
    #Check out Network Analyst license if available. Fail if the Network Analyst license is not available.
    if arcpy.CheckExtension("network") == "Available":
        arcpy.CheckOutExtension("network")
    else:
        raise arcpy.ExecuteError("Network Analyst Extension license is not available.")
    
    #Set environment settings
    output_dir = "C:/Data"
    #The NA layer's data will be saved to the workspace specified here
    env.workspace = os.path.join(output_dir, "Output.gdb")
    env.overwriteOutput = True

    #Set local variables
    input_gdb = "C:/Data/SanFrancisco.gdb"
    network = os.path.join(input_gdb, "Transportation", "Streets_ND")
    layer_name = "FireStationsCoverage"
    travel_mode = "Driving Time"
    cutoffs = [2, 3, 5] #minutes
    field_to_add = "Address"
    field_type = "TEXT"
    facilities = os.path.join(input_gdb, "Analysis", "FireStations")
    search_tolerance = "2 Miles"
    out_featureclass = os.path.join(output_dir, "Output.gdb",
                                                    "FireStationsCoverageArea")

    #Create a new service area analysis layer. For this scenario, the default
    #value for all the remaining parameters statisfies the analysis requirements
    result_object = arcpy.na.MakeServiceAreaAnalysisLayer(network, layer_name,
                                                travel_mode, cutoffs=cutoffs)

    #Get the layer object from the result object. The service area layer can now
    #be referenced using the layer object.
    layer_object = result_object.getOutput(0)

    #Get the names of all the sublayers within the service area layer.
    sublayer_names = arcpy.na.GetNAClassNames(layer_object)
    #Stores the layer names that we will use later
    facilities_layer_name = sublayer_names["Facilities"]
    polygons_layer_name = sublayer_names["SAPolygons"]

    #Add the Address field to the Facilities sublayer of the service area layer.
    #This is done before loading the fire stations as facilities so that the
    #Address values can be transferred from the input features to the
    #Facilities sublayer.
    arcpy.na.AddFieldToAnalysisLayer(layer_object, facilities_layer_name,
                                        field_to_add, field_type)

    #Add the fire station features as Facilities and map the Name and the
    #Address fields from the fire station features to the Name and Address
    #properties on the Facilities sublayer
    field_mappings = arcpy.na.NAClassFieldMappings(layer_object,
                                                    facilities_layer_name)
    field_mappings['Name'].mappedFieldName = "Name"
    field_mappings['Address'].mappedFieldName = "Address"
    arcpy.na.AddLocations(layer_object, facilities_layer_name, facilities,
                          field_mappings, search_tolerance)

    #Solve the service area layer
    arcpy.na.Solve(layer_object)

    #Get the layer objects for all the sublayers within the service area layer
    facilities_sublayer = layer_object.listLayers(facilities_layer_name)[0]
    polygons_sublayer = layer_object.listLayers(polygons_layer_name)[0]

    #Transfer the Address field from the Facilities sublayer to the Polygons
    #sublayer of the service area layer since we wish to export the polygons.
    #The FacilityID field in the Polygons sublayer is related to the ObjectID
    #field in the Facilities sublayer.
    arcpy.management.JoinField(polygons_sublayer, "FacilityID",
                                facilities_sublayer, "ObjectID", field_to_add)

    #Export the Polygons sublayer to a feature class on disk.
    arcpy.management.CopyFeatures(polygons_sublayer, out_featureclass)

    print("Script completed successfully")

except Exception as e:
    # If an error occurred, print line number and error message
    import traceback, sys
    tb = sys.exc_info()[2]
    print("An error occurred on line %i" % tb.tb_lineno)
    print(str(e))

Environments

Licensing information

  • ArcGIS Desktop Basic: Yes
  • ArcGIS Desktop Standard: Yes
  • ArcGIS Desktop Advanced: Yes

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