21 lines
894 B
Markdown
21 lines
894 B
Markdown
|
Find the breaks for N categories in a numerical column based on the [Heads/Tails optimization](http://arxiv.org/pdf/1209.2801v1.pdf). Below, Heads/Tails used to color based on the area of the polygons.
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
#### Using the function
|
||
|
|
|
||
|
|
We can determine the 7 most optimal breaks in a column of numerical data as follows,
|
||
|
|
|
||
|
|
```sql
|
||
|
|
SELECT CDB_HeadsTailsBins(array_agg(numeric_column), 7) FROM table_name
|
||
|
|
-- Results in an ordered array like, {7824,23492,52696,233857,666089,1001709,1638094}
|
||
|
|
-- Each break happens up to, and equal, to a number:
|
||
|
|
-- (bin1 is less than or equal to 7824, bin2 is less than or equal to 23492, etc.)
|
||
|
|
```
|
||
|
|
|
||
|
|
#### Arguments
|
||
|
|
|
||
|
|
CDB_HeadsTailsBins(in_array, breaks)
|
||
|
|
|
||
|
|
* **in_array** numeric[]. A NUMERIC array of values.
|
||
|
|
* **breaks** int. The number of categories you want to create
|