44 lines
1.4 KiB
PL/PgSQL
44 lines
1.4 KiB
PL/PgSQL
--
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-- Determine the Quantile classifications from a numeric array
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--
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-- @param in_array A numeric array of numbers to determine the best
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-- bins based on the Quantile method.
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--
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-- @param breaks The number of bins you want to find.
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--
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--
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CREATE OR REPLACE FUNCTION CDB_QuantileBins ( in_array NUMERIC[], breaks INT) RETURNS NUMERIC[] as $$
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DECLARE
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element_count INT4;
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break_size numeric;
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tmp_val numeric;
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i INT := 1;
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reply numeric[];
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BEGIN
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-- sort our values
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SELECT array_agg(e) INTO in_array FROM (SELECT unnest(in_array) e ORDER BY e ASC) x;
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-- get the total size of our data
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element_count := array_length(in_array, 1);
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break_size := element_count::numeric / breaks;
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-- slice our bread
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LOOP
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IF i < breaks THEN
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IF break_size * i % 1 > 0 THEN
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SELECT e INTO tmp_val FROM ( SELECT unnest(in_array) e LIMIT 1 OFFSET ceil(break_size * i) - 1) x;
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ELSE
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SELECT avg(e) INTO tmp_val FROM ( SELECT unnest(in_array) e LIMIT 2 OFFSET ceil(break_size * i) - 1 ) x;
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END IF;
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ELSIF i = breaks THEN
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-- select the last value
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SELECT max(e) INTO tmp_val FROM ( SELECT unnest(in_array) e ) x;
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ELSE
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EXIT;
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END IF;
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reply = array_append(reply, tmp_val);
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i := i+1;
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END LOOP;
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RETURN reply;
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END;
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$$ language plpgsql IMMUTABLE;
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