--- slug: /en/sql-reference/aggregate-functions/reference/covarpopmatrix sidebar_position: 36 --- # covarPopMatrix Returns the population covariance matrix over N variables. **Syntax** ```sql covarPopMatrix(x[, ...]) ``` **Arguments** - `x` — a variable number of parameters. [(U)Int*](../../data-types/int-uint.md), [Float*](../../data-types/float.md), [Decimal](../../data-types/decimal.md). **Returned Value** - Population covariance matrix. [Array](../../data-types/array.md)([Array](../../data-types/array.md)([Float64](../../data-types/float.md))). **Example** Query: ```sql DROP TABLE IF EXISTS test; CREATE TABLE test ( a UInt32, b Float64, c Float64, d Float64 ) ENGINE = Memory; INSERT INTO test(a, b, c, d) VALUES (1, 5.6, -4.4, 2.6), (2, -9.6, 3, 3.3), (3, -1.3, -4, 1.2), (4, 5.3, 9.7, 2.3), (5, 4.4, 0.037, 1.222), (6, -8.6, -7.8, 2.1233), (7, 5.1, 9.3, 8.1222), (8, 7.9, -3.6, 9.837), (9, -8.2, 0.62, 8.43555), (10, -3, 7.3, 6.762); ``` ```sql SELECT arrayMap(x -> round(x, 3), arrayJoin(covarPopMatrix(a, b, c, d))) AS covarPopMatrix FROM test; ``` Result: ```reference ┌─covarPopMatrix────────────┐ 1. │ [8.25,-1.76,4.08,6.748] │ 2. │ [-1.76,41.07,6.486,2.132] │ 3. │ [4.08,6.486,34.21,4.755] │ 4. │ [6.748,2.132,4.755,9.93] │ └───────────────────────────┘ ```