Calculates the kurtosis (fourth moment) of array elements. Analog of the kurtosis() in R (e1071 library).
const double& array // array with data
[in] Array with data for calculation.
[in] Initial index for calculation.
[in] The number of elements for calculation.
Kurtosis of array elements. In case of error it returns NaN (not a number).
Calculation of the kurtosis is performed using the excess kurtosis around the normal distribution (excess kurtosis=kurtosis-3), i.e. the excess kurtosis of a normal distribution is zero.
It is positive if the peak of the distribution around the expected value is sharp, and negative if the peak is flat.