Résumé
An ArcPy class for performing a location-allocation analysis.
Discussion
A location-allocation analysis allows you to locate facilities in a way that supplies the demand points most efficiently.
Syntaxe
LocationAllocation (in_network)
| Paramètre | Explication | Type de données |
in_network | The network dataset or service that will be used for the network analysis. The argument can be specified using the catalog path to the network dataset, a network dataset layer object, the string name of the network dataset layer, or a portal URL for a network analysis service. The network must have at least one travel mode. To use a portal URL, you must be signed in to the portal with an account that has routing privileges. Solving an analysis will consume credits when the object uses ArcGIS Online as the in_network. For more information, see Service Credits Overview | String |
Propriétés
| Propriété | Explication | Type de données |
| accumulateAttributeNames (Lecture et écriture) | A list of cost attributes to be accumulated during analysis. These accumulated attributes are for reference only; the solver only uses the cost attribute used by your designated travel mode when solving the analysis. The default is an empty list. | String |
| allowSaveLayerFile (Lecture et écriture) | Specifies whether to permit saving the analysis result as a layer file using the saveAsLayerFile method on the result object. A value of True means that you can save a layer file. A value of False means that you cannot. The default is True if the analysis references a network dataset and False if it references a portal service. Allowing a layer file to be saved may slow down the analysis when the analysis references a portal service. | Boolean |
| decayFunctionParameterValue (Lecture et écriture) | Together, the decayFunctionType property and the decayFunctionParameterValue property (β) specify how severely the network impedance between facilities and demand points influences the solver's choice of facilities. Learn more about the Location-Allocation decay function. This property sets the parameter value for the decay function. The default is 1. | Double |
| decayFunctionType (Lecture et écriture) | The decayFunctionType property, or impedance transformation, sets the equation for transforming the network cost between facilities and demand points. This property, together with the decayFunctionParameterValue property (β), species how severely the network impedance between facilities and demand points influences the solver's choice of facilities. Learn more about the Location-Allocation decay function. The property is returned and set as a member of the DecayFunctionType enumeration. The default is DecayFunctionType.Linear. | Object |
| defaultCapacity (Lecture et écriture) | The capacity assigned to all the facilities. This parameter is only applicable when the problemType property is set to LocationAllocationProblemType.MaximizeCapacitatedCoverage. The default is 1. The defaultCapacity can be overridden on a per-facility basis using the Capacity field in the input facilities. | Double |
| defaultImpedanceCutoff (Lecture et écriture) | The maximum impedance at which a demand point can be allocated to a facility. If the travel mode used in the analysis uses a time-based impedance attribute, the defaultImpedanceCutoff is interpreted in the units specified in the timeUnits property. If the travel mode used in the analysis uses a distance-based impedance attribute, the defaultImpedanceCutoff is interpreted in the units specified in the distanceUnits property. If the travel mode's impedance attribute is neither time based nor distance based, the defaultImpedanceCutoff value is interpreted in the units of the impedance attribute. The default is None, which means that no cutoff is applied. The defaultImpedanceCutoff can be overridden on a per-demand-point basis using the TimeCutoff field for a time-based impedance attribute, the DistanceCutoff field for a distance-based impedance attribute, or the Cutoff field if the travel mode's impedance attribute is neither time based nor distance based. | Double |
| distanceUnits (Lecture et écriture) | The units to use when reporting the travel distance in the analysis output. Regardless of the units of the cost attributes in the network dataset, the output will be transformed to and reported in the units set in this property. The property is returned and set as a member of the DistanceUnits enumeration. The default is DistanceUnits.Kilometers. | Object |
| facilityCount (Lecture et écriture) | The number of facilities the solver should choose. The default is 1. This parameter is not applicable for the LocationAllocationProblemType.MaximizeCoverage and LocationAllocationProblemType.TargetMarketShare problem types. | Integer |
| ignoreInvalidLocations (Lecture et écriture) | Specifies whether invalid input locations will be ignored. A value of True indicates that invalid input locations will be ignored so that the analysis will succeed using only valid locations. A value of False indicates that invalid locations will not be ignored and will cause the analysis to fail. Héritage :Routing services based on portals running versions of ArcGIS Enterprise older than 10.9 always ignore invalid input locations. The method returns a ValueError exception if you set ignoreInvalidLocations to False and the service does not support this option. | Boolean |
| lineShapeType (Lecture et écriture) | The type of linear shape to be generated to represent the output of the analysis. The travel time and distance are always calculated along the network; however, the linear output shapes represent the connections calculated between the input points in the analysis rather than the path through the network. The property is returned and set as a member of the LineShapeType enumeration. The default is LineShapeType.StraightLine. | Object |
| networkDataSource (Lecture seule) | The full catalog path to the network dataset used for the analysis. | String |
| overrides (Lecture et écriture) | Specify additional settings that can influence the behavior of the solver when finding solutions for the network analysis problems. The value for this parameter must be specified in JavaScript Object Notation (JSON). For example, a valid value is of the following form: {"overrideSetting1" : "value1", "overrideSetting2" : "value2"}. The override setting name is always enclosed in double quotation marks. The values can be either a number, Boolean, or string. The default value for this parameter is no value, which indicates to not override any solver settings. Overrides are advanced settings that should be used only after careful analysis of the results obtained before and after applying the settings. A list of supported override settings for each solver and their acceptable values can be obtained by contacting Esri Technical Support. | String |
| problemType (Lecture et écriture) | The problem type to use for the analysis. Learn more about Location-Allocation problem types. The property is returned and set as a member of the LocationAllocationProblemType enumeration. The default is LocationAllocationProblemType.MinimizeImpedance. | Object |
| searchQuery (Lecture et écriture) | When locating inputs on the network, specifies a query to restrict the search to a subset of the features within a source feature class. This is useful if you don't want to find features that may be unsuited for a network location. For example, if you are loading centroids of polygons and don't want to locate on local roads, you can define a query that searches for major roads only. Learn more about locating inputs on the network The parameter value is specified as a list with nested lists. The nested list is composed of two values indicating the name and the SQL expression for all of the network sources. The syntax for the SQL expression differs slightly depending on the type of the network source feature class. For example, if you're querying source feature classes stored in file or enterprise geodatabases, shapefiles, or SDC, enclose field names in double quotation marks: "CFCC". If you're querying source feature classes stored in personal geodatabases, enclose fields in square brackets: [CFCC]. If you don't want to specify a query for a particular source, use "#" as the value for the SQL expression or exclude the source name and the SQL expression from the parameter value. If you don't want to specify a query for all of the network sources, use "#" as the parameter value. For example, the parameter value [["Streets","\"CFCC\" = 'A15'"], ["Streets_ND_Junctions",""]] specifies an SQL expression for the Streets source feature class and no expression for the Streets_ND_Junctions source feature class. Note that the double quotation marks used to enclose the field name CFCC are escaped using backslash characters to avoid a parsing error from the Python interpreter. By default, no query is used. | List |
| searchTolerance (Lecture et écriture) | The maximum search distance to use when locating the input features on the network. The property is returned and set as a double, and the units of this value are accessed through the searchToleranceUnits property. The default is 5000. | Double |
| searchToleranceUnits (Lecture et écriture) | The units of the searchTolerance property. The property is returned and set as a member of the DistanceUnits enumeration. The default is DistanceUnits.Meters. | Object |
| targetMarketShare (Lecture et écriture) | The percentage of the total demand weight that you want your solution facilities to capture. The solver chooses the minimum number of facilities required to capture the target market share specified by this numeric value. The default is 10, and the value must be between 0 and 100. This parameter is only applicable when the problemType property is set to LocationAllocationProblemType.TargetMarketShare. | Double |
| timeOfDay (Lecture et écriture) | The time of day to use for the analysis. The default is None, which means that the analysis will be time neutral. | DateTime |
| timeUnits (Lecture et écriture) | The units to use when reporting the travel time in the analysis output. Regardless of the units of the cost attributes in the network dataset, the outputs will be transformed to and reported in the units set in this property. The property is returned and set as a member of the TimeUnits enumeration. The default is TimeUnits.Minutes. | Object |
| timeZone (Lecture et écriture) | Indicates whether the time specified in the timeOfDay property will be interpreted as the local time at the input locations or as coordinated universal time (UTC). The property is returned and set as a member of the TimeZoneUsage enumeration and is applicable only when the timeOfDay property is not None. The default is TimeZoneUsage.LocalTimeAtLocations. | Object |
| travelDirection (Lecture et écriture) | The direction of travel between facilities and demand points. The property is returned and set as a member of the TravelDirection enumeration. The default is TravelDirection.FromFacility. | Object |
| travelMode (Lecture et écriture) | The travel mode to use for the analysis. The value is returned and set as an arcpy.nax.TravelMode object, but it can also be set using the string name of the travel mode or a string containing the valid JSON representation of a travel mode. The default is the default travel mode defined on the network dataset used for the analysis. | Object |
Vue d’ensemble des méthodes
| Méthode | Explication |
| addFields (input_type, field_description) | Adds custom fields to the designated input class. These fields will be included in the field mapping dictionary created by the fieldMappings method and will also be available for use with the insertCursor method. |
| count (input_type) |
Returns the number of rows added for an input type. |
| fieldMappings (input_type, {use_location_fields}, {list_candidate_fields}) | Generates an NAClassFieldMappings dictionary that maps the field names of the input type to arcpy.nax.NAClassFieldMap objects that allow you to map fields from your input data to the properties of the solver. The dictionary can be used as input to the load method's field_mappings argument. |
| fieldNames (input_type, {use_location_fields}) | Get a list of field names supported by the specified input type. |
| insertCursor (input_type, field_names, {append}) | Establishes a write cursor on the specified input type. This cursor can be used to add rows directly to the input. |
| load (input_type, features, {field_mappings}, {append}, {max_features}) | Set input features to use for the analysis. |
| solve () | Perform the location-allocation analysis using the properties set on the LocationAllocation object and the loaded inputs. |
Méthodes
addFields (input_type, field_description)
| Paramètre | Explication | Type de données |
input_type |
The type of input to which the fields should be added. The parameter should be set using the LocationAllocationInputDataType enumeration. | Object |
field_description [field_description,...] |
The fields and their properties that will be added to the input class. The value should be constructed as a list of lists with each row containing the following items:
Available field types are as follows:
The method will return an error if the field already exists in the table or if any of the field properties are invalid. | List |
count (input_type)
| Paramètre | Explication | Type de données |
input_type | The type of input features to count. The parameter should be set using the LocationAllocationInputDataType enumeration. | Object |
| Type de données | Explication |
| Integer | The number of rows. |
fieldMappings (input_type, {use_location_fields}, {list_candidate_fields})| Paramètre | Explication | Type de données |
input_type | The type of input for which the field mappings are returned. The parameter should be set using the LocationAllocationInputDataType enumeration. See descriptions of the fields available for each input type | Object |
use_location_fields | Indicates whether network location fields should be included in the returned field mappings dictionary. Network location fields describe the point on the network where an object is located. You can use network location fields to more precisely control how your analysis inputs locate on the network and to save time when calling the solve method because the solver will not have to calculate the location fields from the geometry of the inputs. You can calculate location fields for a feature class using the Calculate Locations tool. Learn more about network location fields and how inputs are located on the network When this argument is set to True, the returned field mappings dictionary will contain network location fields. The default is False; the field mapping dictionary will not include network location fields. (La valeur par défaut est False) | Boolean |
list_candidate_fields [list_candidate_fields,...] | Use this parameter to map additional, non-default fields from your input data into your analysis inputs. For example, if your input feature class contains a field named MyField, and you want this field to be included in your analysis inputs, pass the MyField field object to the list_candidate_fields parameter. MyField will be included in the returned field mapping dictionary and automatically mapped. When you call the load method using these field mappings, MyField will be included in the analysis inputs along with all the default fields. In many cases, these extra fields will be passed to the analysis output as well. The parameter should be specified as a list of arcpy.Field objects, which can be obtained from a given feature class or table using the arcpy.ListFields function. Learn more about best practices for setting up analysis inputs (La valeur par défaut est None) | Field |
| Type de données | Explication |
| Dictionary | An NAClassFieldMappings dictionary in which the keys are the field names and values are arcpy.nax.NAClassFieldMap objects. |
fieldNames (input_type, {use_location_fields})| Paramètre | Explication | Type de données |
input_type | The type of input for which the supported field names are returned. The parameter should be set using the LocationAllocationInputDataType enumeration. See descriptions of the fields available for each input type | Object |
use_location_fields | Indicates whether network location fields will be included in the returned list of field names. Network location fields describe the point on the network where an object is located. You can use network location fields to more precisely control how your analysis inputs locate on the network and to save time when calling the solve method because the solver will not have to calculate the location fields from the geometry of the inputs. You can calculate location fields for a feature class using the Calculate Locations tool. Learn more about network location fields and how inputs are located on the network When this argument is set to True, the returned list of field names will contain network location fields. The default is False; the list of field names will not include network location fields. (La valeur par défaut est False) | Boolean |
| Type de données | Explication |
| String | A list of field names supported by the specified input type. |
insertCursor (input_type, field_names, {append})| Paramètre | Explication | Type de données |
input_type | The type of input into which the cursor can be used to insert rows. The parameter should be set using the LocationAllocationInputDataType enumeration. | Object |
field_names [field_names,...] | A list of field names of the input type whose values you want to set when inserting rows using the cursor. You can get the names of the fields supported by an input type by using the fieldNames method. See descriptions of the fields available for each input type In addition to regular fields, you can also set the geometry of the input using one of the following geometry tokens:
The SHAPE@XY and SHAPE@XYZ tokens are only supported for point-based input types. When using the SHAPE@XY and SHAPE@XYZ tokens, the x-, y-, and z-values should be specified in the spatial reference of the network data source being used in the analysis. | String |
append | Specifies whether the features being inserted should be appended to the existing set of features for the input type. A value of True indicates that the new features should be appended; the existing features will be preserved. This is the default. A value of False indicates that any existing features for the input type should be deleted and replaced with the features currently being inserted. (La valeur par défaut est True) | Boolean |
| Type de données | Explication |
| Object | A SolverInsertCursor object that can be used to write features. |
load (input_type, features, {field_mappings}, {append}, {max_features})| Paramètre | Explication | Type de données |
input_type | The type of input feature to load. The parameter should be set using the LocationAllocationInputDataType enumeration. | Object |
features | The input features to load. This parameter accepts the following input types:
For layer inputs, only selected features will be loaded. If a layer has a definition query, only the subset of features visible with the definition query will be loaded. The method also honors the Extent geoprocessing environment; only features in the specified extent will be loaded. | String |
field_mappings | An NAClassFieldMappings dictionary that maps the field names of the input type to arcpy.nax.NAClassFieldMap objects representing the mapping of fields from the input features. Valid input for this parameter can be constructed using the fieldMappings method. If field mappings are not specified, all fields from the input features that have the same name as the supported fields for the input type will be mapped. (La valeur par défaut est None) | Dictionary |
append | Indicates whether the features being loaded should be appended to the existing set of features for the input type. A value of True indicates that the new features should be appended; the existing features will be preserved. This is useful if you want to load inputs from multiple feature classes or tables to use in a single analysis. This is the default. A value of False indicates that any existing features for the input type should be deleted and replaced with the features currently being loaded. (La valeur par défaut est True) | Boolean |
max_features | The maximum number of features that can be loaded into the input type. This is useful if you are creating a tool or service and want an error returned if the size of the input exceeds the available resources. The load method will return an arcpy.nax.LimitError if the number of input features exceeds the max_features limit. If a value is not specified, no limit is enforced for the count of the input features. (La valeur par défaut est None) | Integer |
solve ()
| Type de données | Explication |
| Object | An arcpy.nax.LocationAllocationResult object that can be used to access outputs and solver messages. |
Exemple de code
Perform location-allocation analysis.
# An example showing how to perform location-allocation analysis using inputs from feature classes.
import arcpy
arcpy.CheckOutExtension("network")
nds = "C:/data/NorthAmerica.gdb/Routing/Routing_ND"
nd_layer_name = "Routing_ND"
input_facilities = "C:/data/io.gdb/Facilities"
input_demand_points = "C:/data/io.gdb/DemandPoints"
output_lines = "C:/data/io.gdb/AllocationLines"
# Create a network dataset layer and get the desired travel mode for analysis
arcpy.nax.MakeNetworkDatasetLayer(nds, nd_layer_name)
nd_travel_modes = arcpy.nax.GetTravelModes(nd_layer_name)
travel_mode = nd_travel_modes["Driving Time"]
# Instantiate a LocationAllocation solver object
loc_alloc = arcpy.nax.LocationAllocation(nd_layer_name)
# Set properties
loc_alloc.travelMode = travel_mode
loc_alloc.travelDirection = arcpy.nax.TravelDirection.ToFacility
loc_alloc.problemType = arcpy.nax.LocationAllocationProblemType.MinimizeImpedance
loc_alloc.facilityCount = 3
loc_alloc.timeUnits = arcpy.nax.TimeUnits.Minutes
loc_alloc.defaultImpedanceCutoff = 15
loc_alloc.lineShapeType = arcpy.nax.LineShapeType.StraightLine
# Load inputs
loc_alloc.load(arcpy.nax.LocationAllocationInputDataType.Facilities, input_facilities)
loc_alloc.load(arcpy.nax.LocationAllocationInputDataType.DemandPoints, input_demand_points)
# Solve the analysis
result = loc_alloc.solve()
# Export the results to a feature class
if result.solveSucceeded:
result.export(arcpy.nax.LocationAllocationOutputDataType.Lines, output_lines)
else:
print("Solve failed")
print(result.solverMessages(arcpy.nax.MessageSeverity.All))Vous avez un commentaire à formuler concernant cette rubrique ?