/* -----------------------------------------------------------------------------
 * Test Mann-Whitney-test.
 * 
 * Example taken from:
 * http://www.itl.nist.gov/div898/handbook/prc/section3/prc35.htm
 * -------------------------------------------------------------------------- */

m4_include(`SQLCommon.m4')
m4_changequote(<!,!>)
m4_ifdef(<!__HAS_ORDERED_AGGREGATES__!>,<!

CREATE TABLE nist_mw_example (
	id SERIAL,
	group_a FLOAT8,
	rank_a FLOAT8,
	group_b FLOAT8,
	rank_b FLOAT8
);

COPY nist_mw_example(group_a, rank_a, group_b, rank_b) FROM stdin;
.55	8	.49	5
.67	15.5	.68	17
.43	1	.59	9.5
.51	6	.72	19
.48	3.5	.67	15.5
.60	11	.75	20.5
.71	18	.65	13.5
.53	7	.77	22
.44	2	.62	12
.65	13.5	.48	3.5
.75	20.5	.59	9.5
\.

CREATE TABLE mw_test AS
SELECT (mw_test(from_first, value ORDER BY value)).*
FROM (
    SELECT TRUE AS from_first, group_a AS value
    FROM nist_mw_example
    UNION ALL
    SELECT FALSE, group_b
    FROM nist_mw_example
) q;

SELECT * FROM mw_test;
SELECT assert(
    relative_error(statistic, -1.346133) < 0.001 AND
    u_statistic = 40 AND
    relative_error(p_value_one_sided, 1 - 0.089130) < 0.001,
    'Mann-Whitney test: Wrong results'
) FROM mw_test;

!>)
m4_changequote(<!`!>,<!'!>)