Stddev

Standard deviation

Signature

stddev(expr: AttrName|(Tuple->Numeric)) -> Aggregator

Examples

stddev(:qty)

stddev{|t| t.qty * t.price }

stddev(->(t){ t.qty * t.price })

Description

Computes how much variation from the average exists.

Implementation notes

This aggregate function should only be used with numeric types. As of current Alf version, it does not aggregate empty sets correctly on non-numeric data types.