向分析图层添加字段 (网络分析)

摘要

向网络分析图层的子图层添加字段

用法

• 该工具通常与添加位置工具配合使用，以将输入要素中的字段传递到子图层。例如，如果想要将输入要素中名为 UniqueID 的字段传递到“服务区”图层的“设施点”子图层，请使用该工具先将 UniqueID 字段添加到“设施点”子图层，然后使用添加位置工具中的字段映射为 UniqueID 字段提供输入值。

• 可以为网络分析图层的任意子图层添加字段。

语法

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

参数	说明	数据类型
in_network_analysis_layer	要添加新字段的网络分析图层。	Network Analyst Layer
sub_layer	要添加新字段的网络分析图层的子图层。	String
field_name	要添加到网络分析图层的指定子图层中的字段名称。	String
field_type	在创建新字段时使用的字段类型。 LONG —特定范围内不含小数值的数值。 TEXT —名称或其他文本特性。 FLOAT —特定范围内含小数值的数值。 DOUBLE —特定范围内含小数值的数值。 SHORT —特定范围内不含小数值的数值；编码值。 DATE —日期和/或时间。 BLOB —影像或其他多媒体。	String
field_precision （可选）	描述可存储在字段中的位数。所有位都将被计算在内，而无论其处于小数点的哪一侧。 参数值仅适用于数字字段类型。	Long
field_scale （可选）	设置可存储在字段中的小数位数。此参数仅可用于浮点型和双精度数据字段类型。	Long
field_length （可选）	要添加的字段的长度。它为字段的每条记录设置最大允许字符数。此选项仅适用于文本或 blob 类型的字段。	Long
field_alias （可选）	指定给字段名称的备用名称。此名称用于为含义隐晦的的字段名称指定更具描述性的名称。字段别名参数仅适用于地理数据库和 coverage。	String
field_is_nullable （可选）	不存在关联属性信息的地理要素。它们与零或空字段不同，仅支持地理数据库中的字段。 NON_NULLABLE —字段不允许空值。 NULLABLE —字段允许空值。这是默认设置。	Boolean

代码示例

AddFieldToAnalysisLayer 示例 1（Python 窗口）

下面的 Python 窗口脚本演示了如何将 UniqueID 字段添加到“服务区”网络分析图层的“设施点”子图层。

import arcpy
arcpy.AddFieldToAnalysisLayer_na("Service Area","Facilities","UniqueID","LONG")

AddFieldToAnalysisLayer 示例 2（工作流）

下面的独立 Python 脚本演示了如何使用 AddFieldToAnalysisLayer 函数将 StationID 字段从输入消防站要素传递到通过服务区分析计算出的 2、3、5 分钟服务区面要素。StationID 字段可用于将消防站要素的其他属性连接到服务区面要素。

# Name: AddFieldToAnalysisLayer_Workflow.py
# Description: Transfers the StationID field from the input fire station 
#              features to the 2,3,5 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.
# Requirements: Network Analyst Extension 

#Import system modules
import arcpy
from arcpy import env

try:
    #Check out the Network Analyst extension license
    arcpy.CheckOutExtension("Network")

    #Set environment settings
    env.workspace = "C:/data/SanFrancisco.gdb"
    env.overwriteOutput = True
    
    #Set local variables
    inNetworkDataset = "Transportation/Streets_ND"
    outNALayer = "FireStationsCoverage"
    impedanceAttribute = "TravelTime"
    defaultBreakValues = "2 3 5"   
    fieldName = "StationID"
    fieldType = "LONG"
    inFeatures = "Analysis/FireStations"
    fieldMappings = "Name StationName #; StationID StationID #"
    searchTolerance = "2 Miles"
    polygonLayer = outNALayer + "/" + "Polygons"
    facilitiesLayer = outNALayer + "/" + "Facilities"
    calculateField = "SAPolygons." + fieldName    
    expression = "!Facilities." + fieldName + "!"
    outFeatures = outNALayer + "Area"
    
    #Create a new service area analysis layer. For this scenario, the default 
    #value for all the remaining parameters statisfies the analysis requirements
    arcpy.MakeServiceAreaLayer_na(inNetworkDataset, outNALayer,
                                  impedanceAttribute,"",defaultBreakValues)
    
    #Add a StationID field to the Facilities sublayer of the service area layer.
    #This is done before loading the fire stations as facilities so that the 
    #StationID values can be transferred from the input features to the 
    #Facilities sublayer. The service area layer created previously is 
    #referred by its name.
    arcpy.AddFieldToAnalysisLayer_na(outNALayer,"Facilities",fieldName,
                                     fieldType)
    
    #Add the fire station features as Facilities and map the Name and the 
    #StationID properties from the StationName and StationID fields.
    arcpy.AddLocations_na(outNALayer,"Facilities",inFeatures,fieldMappings,
                          searchTolerance)
    
    #Solve the service area layer
    arcpy.Solve_na(outNALayer)
    
    #Transfer the StationID field from Facilities sublayer to Polygons sublayer 
    #of the service area layer since we wish to export the polygons.
    #First add "StationID" field to the Polygons sublayer
    arcpy.AddFieldToAnalysisLayer_na(outNALayer,"Polygons",fieldName,fieldType)
    
    #Join Facilities to Polygons based on FacilityID and ObjectID fields
    arcpy.AddJoin_management(polygonLayer,"FacilityID",facilitiesLayer,
                            "ObjectID")
    
    #Calculate the StationID field in Polygons based on the StationID field from
    #facilities.
    arcpy.CalculateField_management(polygonLayer,calculateField,expression,
                                    "PYTHON")
    
    #Remove the join so that the Polygons sublayer will not have all the fields 
    #from the Facilities sublayer when Polygons are exported to a feature class.
    arcpy.RemoveJoin_management(polygonLayer,"Facilities")
    
    #Export the Polygons sublayer to a feature class on disk.
    arcpy.CopyFeatures_management(polygonLayer, outFeatures)
    
    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 occured on line %i" % tb.tb_lineno
    print str(e)

    
    
    
    
    
                                  
                                  

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