kurtosis_y() | kurtosis_x()

Since 1.3.0

Calculate the kurtosis from a two-dimensional statistical aggregate for the given dimension. For example, kurtosis_y() calculates the kurtosis for all the values of the y variable, independent of values of the x variable. The kurtosis is the fourth statistical moment. It is a measure of “tailedness” of a data distribution compared to a normal distribution.

Samples

Calculate the kurtosis of a sample containing the integers from 0 to 100:

SELECT kurtosis_y(stats_agg(data, data))
  FROM generate_series(0, 100) data;

This returns something like:

kurtosis_y
----------
1.78195

Arguments

The syntax is:

kurtosis_y(
  summary StatsSummary2D,
  [ method TEXT ]
) RETURNS DOUBLE PRECISION

kurtosis_x(
  summary StatsSummary2D,
  [ method TEXT ]
) RETURNS DOUBLE PRECISION

Name	Type	Default	Required	Description
summary	StatsSummary2D	-	✔	The statistical aggregate produced by a stats_agg call
method	TEXT	sample	-	The method used for calculating the kurtosis. The two options are population and sample, which can be abbreviated to pop or samp

Returns

Column	Type	Description
kurtosis_y	kurtosis_x	DOUBLE PRECISION