KURT,KURT_POP,KURTOSIS

Description

The KURTOSIS function returns the kurtosis of the expr expression. The forumula used for this function is 4-th centrol moment / ((variance)^2) - 3.

Alias

KURT_POP,KURTOSIS

Syntax

KURTOSIS(<expr>)

Parameters

Parameters	Description
<expr>	The expression needs to be obtained

Return Value

Returns a value of type DOUBLE. Special cases:

• Returns NULL when the variance is zero.

Example

select * from statistic_test;

+-----+------+------+
| tag | val1 | val2 |
+-----+------+------+
|   1 |  -10 |   -10|
|   2 |  -20 |  NULL|
|   3 |  100 |  NULL|
|   4 |  100 |  NULL|
|   5 | 1000 |  1000|
+-----+------+------+

select kurt(val1), kurt(val2) from statistic_test;

+-------------------+--------------------+
| kurt(val1)        | kurt(val2)         |
+-------------------+--------------------+
| 0.162124583734851 | -1.3330994719286338 |
+-------------------+--------------------+

// Each group just has one row, result is NULL
select kurt(val1), kurt(val2) from statistic_test group by tag;

+------------+------------+
| kurt(val1) | kurt(val2) |
+------------+------------+
|       NULL |       NULL |
|       NULL |       NULL |
|       NULL |       NULL |
|       NULL |       NULL |
|       NULL |       NULL |
+------------+------------+