Skater

TerraAmazon provides a tool for area regionalization to group small areas (such as municipalities and neighborhoods) in larger contiguous areas where associated attributes are similar to the small areas (such as homicides and kidnappings). TerraAmazon tool for this task is the SKATER tool.

The Skater (Spatial "k"luster Analysis by Tree Edge Removal) method is a cluster analysis that considers the spatial localization of objects. It is applied when a map is partitioned in areas, each one with a given geographic localization, and areas with similar characteristics must be part of the same spatial grouping. The characteristics are obtained by values of measured variables.

The variables are standardized due to the different impact scales may have in the dissimilarity function and in the sum of squares in the clusters. Therefore, variables to be used for regionalization have a standard scale with mean zero and standard deviation one. The standardization was obtained by subtracting the average from the original value and dividing by the standard deviation.

Aggregation Method

Choose the criteria to define the number of larger regions (groups) to be created. Clusters option allows the definition of a fixed number and Population option allows the definition of a minimum population for each group.

Attribute Selection

Select the information to be used to calculate similarity among areas. Layer Attributes list displays all allowed (numeric) attributes and Selected Attributes list displays the attributes selected for clustering.

It is accessible through:

PROCESSING → SPATIAL ANALYSIS → SKATER


Input Information:

Layer Name: Select the input layer.

Load GPM: Loads a gpm from file, if not, creates a new one.

Attribute Link: Defines the attribute that identifies the objects of this layer.

GPM: Opens a dialog to select a file with a desired proximity matrix.

Parameters:

Aggregation tab:

Clusters

Number of Clusters: Value that defines the total number of clusters generated in skater operation.

Population

Minimum Population: Value used to define the minimum population in each cluster.

Population Attribute: Attribute from input data that represents the population information.

Skater By Groups: Uses an attribute for grouping the clusters.

Attributes tab:

Layer Attributes: List of all valid attributes that could be used to compute the skater.

Selected Attributes: List of selected attributes used to compute the skater.

Output Information:

Repository: Select one type of repository by clicking on the button to save the output layer as a file or on the button to save it in the database.

Layer Name: Defines the name to create the output layer.

Click on the OK button and then the skater will be calculated.