Analytical Queries - Aggregate Variables

Any variables bound in the where clauses, can be used in conjunction with aggregate functions. For example, the below query takes the sum of ?nums.

{
  "select": "(sum ?nums)",
  "where": [["$fdb8", ["person/handle", "zsmith"], "person/favNums", "?nums"]]
}

The full list of available variables is below:

Function	Description
`avg`	Returns the average of the values.
`count`	Returns a count of the values.
`count-distinct`	Returns a count of the distinct values.
`distinct`	Returns all of the distinct values.
`max`	Returns the largest value.
`median`	Returns the median of the values.
`min`	Returns the smallest value.
`rand`	Returns a random value from the specified values.
`sample`	Given a sample size and a set of values, returns an appropriately sized sample, i.e. `(sample 2 ?age)` returns two ages from values bound to the variable, `?age`.
`stddev`	Returns the standard deviation of the values.
`sum`	Returns the sum of the values.
`variance`	Returns the variance of the values.

Modify the above query, to take a random number from ?nums.