63 lines
2.1 KiB
Markdown
63 lines
2.1 KiB
Markdown
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## K-Means Functions
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### CDB_KMeans(subquery text, no_clusters INTEGER)
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This function attempts to find n clusters within the input data. It will return a table to CartoDB ids and
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the number of the cluster each point in the input was assigend to.
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#### Arguments
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| Name | Type | Description |
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|------|------|-------------|
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| subquery | TEXT | SQL query that exposes the data to be analyzed (e.g., `SELECT * FROM interesting_table`). This query must have the geometry column name `the_geom` and id column name `cartodb_id` unless otherwise specified in the input arguments |
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| no\_clusters | INTEGER | The number of clusters to try and find |
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#### Returns
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A table with the following columns.
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| Column Name | Type | Description |
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|-------------|------|-------------|
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| cartodb\_id | INTEGER | The CartoDB id of the row in the input table.|
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| cluster\_no | INTEGER | The cluster that this point belongs to. |
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#### Example Usage
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```sql
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SELECT
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customers.*,
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km.cluster_no
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FROM cdb_crankshaft.CDB_Kmeans('SELECT * from customers' , 6) km, customers_3
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WHERE customers.cartodb_id = km.cartodb_id
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```
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### CDB_WeightedMean(subquery text, weight_column text, category_column text)
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Function that computes the weighted centroid of a number of clusters by some weight column.
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### Arguments
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| Name | Type | Description |
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|------|------|-------------|
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| subquery | TEXT | SQL query that exposes the data to be analyzed (e.g., `SELECT * FROM interesting_table`). This query must have the geometry column and the columns specified as the weight and category columns|
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| weight\_column | TEXT | The name of the column to use as a weight |
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| category\_column | TEXT | The name of the column to use as a category |
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### Returns
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A table with the following columns.
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| Column Name | Type | Description |
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|-------------|------|-------------|
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| the\_geom | GEOMETRY | A point for the weighted cluster center |
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| class | INTEGER | The cluster class |
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### Example Usage
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```sql
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SELECT ST_TRANSFORM(the_geom, 3857) as the_geom_webmercator, class
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FROM cdb_weighted_mean('SELECT *, customer_value FROM customers','customer_value','cluster_no')
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```
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