Package description

eofs is a Python package for EOF analysis of spatial-temporal data. Using EOFs (empirical orthogonal functions) is a common technique to decompose a signal varying in time and space into a form that is easier to interpret in terms of spatial and temporal variance. Some of the key features of eofs are:

  • Suitable for large data sets: computationally efficient for the large output data sets of modern climate models.

  • Transparent handling of missing values: missing values are removed automatically during computations and placed back into output fields.

  • Automatic metadata: metadata from input fields is used to construct metadata for output fields.

  • No Compiler required: a fast implementation written in pure Python using the power of numpy, no Fortran or C dependencies.

Download and installation

The core of the package runs on Python 2 or 3, on Linux, Windows or OSX; basically anywhere Python+NumPy are available. The iris, and xarray interfaces are available on all platforms where their respective supporting packages iris and xarray can be installed.

eofs can be installed for all platforms using conda:

conda install -c conda-forge eofs

or using pip:

pip install eofs

The source code for released versions of eofs can be downloaded from Github. You must have setuptools installed in order to install eofs from source. After downloading the source code archive, unzip it and change into the unzipped archive’s directory, then to install it:

python setup.py install

You can also check out the source code for the development version from the github repository to access features which are not yet in a release.

Getting started

eofs provides various interfaces for EOF analysis: a standard interface for analysing data contained in either numpy arrays or dask arrays, suitable for any data set; and meta-data interfaces suitable for analysing data read from self-describing files, using the iris or xarray packages. All the interfaces support the same set of operations.

Regardless of which interface you use, the basic usage is the same. The EOF analysis is handled by a solver class, and the EOF solution is computed when the solver class is created. Method calls are then used to retrieve the quantities of interest from the solver class.

The following is a very simple illustrative example which computes the leading 2 EOFs of a temporal spatial field using the eofs.iris interface:

import iris
from eofs.iris import Eof

# read a spatial-temporal field, time must be the first dimension
sst = iris.load_cube('sst_monthly.nc')

# create a solver class, taking advantage of built-in weighting
solver = Eof(sst, weights='coslat')

# retrieve the first two EOFs from the solver class
eofs = solver.eofs(neofs=2)

More detailed description of usage are found in the User Guide or the Examples.

Requirements

This package requires as a minimum that you have numpy available, and requires setuptools for installation. The dask package is an optional dependency that will be used if dask.array is available and dask arrays are provided to the solver. The eofs.iris meta-data enabled interface can only be used if the iris package is available at version 1.2 or higher. The eofs.xarray meta-data enabled interface can only be used if the xarray package is installed.

Citation

If you use eofs in published research, please cite it by referencing the peer-reviewed paper. You can additionally cite the Zenodo DOI if you need to cite a particular version (but please also cite the paper, it helps me justify my time working on this and similar projects).

Developing and contributing

Contributions big or small are welcomed from anyone with an interest in the project. Bug reports and feature requests can be filed using the Github issues system. If you would like to contribute code or documentation please see the Developer Guide.