math:covariance-p

math:covariance-p(
   $arg as json:array*
) as xs:double?

Summary

Returns the population covariance of a data set. The size of the input array should be 2. The function eliminates all pairs for which either the first element or the second element is empty. After the elimination, if the length of the input is 0, the function returns the empty sequence.

For the version of this that uses range indexes, see cts:covariance-p.

Example

  let $array :=
    for $i in (1 to 10)
    let $j := 2*$i
    return json:to-array(($i,$j))

  return math:covariance-p($array)

  => 16.5