.. _General-custom_aggregation:


Calculating a custom statistic
==============================

This example shows how to define and use a custom
:class:`iris.analysis.Aggregator`, that provides a new statistical operator for
use with cube aggregation functions such as :meth:`~iris.cube.Cube.collapsed`,
:meth:`~iris.cube.Cube.aggregated_by` or
:meth:`~iris.cube.Cube.rolling_window`.

In this case, we have a 240-year sequence of yearly average surface temperature
over North America, and we want to calculate in how many years these exceed a
certain temperature over a spell of 5 years or more.



.. plot:: examples/General/custom_aggregation.py
    :include-source: