.. _General-SOI_filtering:


Applying a filter to a time-series
==================================

This example demonstrates low pass filtering a time-series by applying a
weighted running mean over the time dimension.

The time-series used is the Darwin-only Southern Oscillation index (SOI),
which is filtered using two different Lanczos filters, one to filter out
time-scales of less than two years and one to filter out time-scales of
less than 7 years.

References
----------

    Duchon C. E. (1979) Lanczos Filtering in One and Two Dimensions.
    Journal of Applied Meteorology, Vol 18, pp 1016-1022.

    Trenberth K. E. (1984) Signal Versus Noise in the Southern Oscillation.
    Monthly Weather Review, Vol 112, pp 326-332



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

