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

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

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Arguments

NameTypeDefaultRequiredDescription
summaryStatsSummary2D-✔The statistical aggregate produced by a stats_agg call
methodTEXTsample-The method used for calculating the kurtosis. The two options are population and sample, which can be abbreviated to pop or samp

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Returns

ColumnTypeDescription
kurtosis_y | kurtosis_xDOUBLE PRECISIONThe kurtosis of the values in the statistical aggregate

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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;

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