32 lines
1.1 KiB
PL/PgSQL
32 lines
1.1 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 $$
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DECLARE
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element_count INT4;
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break_size numeric;
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tmp_val numeric;
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i INT := 1;
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reply numeric[];
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BEGIN
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-- get our unique values
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SELECT array_agg(e) INTO in_array FROM (SELECT unnest(in_array) e GROUP BY e ORDER BY e ASC) x;
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-- get the total size of our row
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element_count := array_upper(in_array, 1) - array_lower(in_array, 1);
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break_size := element_count::numeric / breaks;
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-- slice our bread
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LOOP
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IF i > breaks THEN EXIT; END IF;
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SELECT e INTO tmp_val FROM ( SELECT unnest(in_array) e LIMIT 1 OFFSET round(break_size * i)) x;
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reply = array_append(reply, tmp_val);
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i := i+1;
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END LOOP;
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RETURN reply;
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END;
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$$ language plpgsql IMMUTABLE; |