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CORR

Description​

Calculates the Pearson correlation coefficient between two random variables.

Syntax​

CORR(<expr1>, <expr2>)

Parameters​

ParametersDescription
<expr1>Expression for calculation. Supported type is Double.
<expr2>Expression for calculation. Supported type is Double.

Return Value​

Returns a DOUBLE type value, which is the covariance of expr1 and expr2 divided by the product of their standard deviations. Special cases:

  • If the standard deviation of expr1 or expr2 is 0, returns 0.
  • If expr1 or expr2 contains NULL values, those rows are excluded from the calculation.
  • If there is no valid data in the group, returns NULL.

Example​

-- setup
create table test_corr(
id int,
k1 double,
k2 double
) distributed by hash (id) buckets 1
properties ("replication_num"="1");

insert into test_corr values
(1, 20, 22),
(1, 10, 20),
(2, 36, 21),
(2, 30, 22),
(2, 25, 20),
(3, 25, NULL),
(4, 25, 21),
(4, 25, 22),
(4, 25, 20);
select id,corr(k1,k2) from test_corr group by id;
+------+--------------------+
| id | corr(k1, k2) |
+------+--------------------+
| 4 | 0 |
| 1 | 1 |
| 3 | NULL |
| 2 | 0.4539206495016019 |
+------+--------------------+
select corr(k1,k2) from test_corr where id=999;

When the query result is empty, returns NULL.

+-------------+
| corr(k1,k2) |
+-------------+
| NULL |
+-------------+