23 lines
1.1 KiB
Markdown
23 lines
1.1 KiB
Markdown
Find the breaks for N categories in a numerical column based on the [Jenks optimization](http://en.wikipedia.org/wiki/Jenks_natural_breaks_optimization). Below, Jenks used to color based on the area of the polygons.
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#### Using the function
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We can determine the 7 most optimal breaks in a column of numerical data as follows,
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```sql
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SELECT CDB_JenksBins(array_agg(numeric_column), 7) FROM table_name
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-- Results in an ordered array like, {0,73,2568,9408,29411,768230,1638094}
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-- Each break happens up to, and equal, to a number:
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-- (bin1 is less than or equal to 0, bin2 is less than or equal to 73, etc.)
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```
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#### Arguments
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CDB_JenksBins(in_array, breaks, invert)
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* **in_array** numeric[]. A NUMERIC array of values.
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* **breaks** int. The number of categories you want to create
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* **iterations** OPTIONAL int. The number of iterations used for calculating breaks.
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* **invert** OPTIONAL boolean. Flips whether you receive top down breaks or bottom up breaks. Default is top down (so, <=). Bottom up would give you values that define the lower-end start of a bin (so >=). |