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APSG - The package for structural geologists

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What is APSG?

APSG is package for structural geologists. It defines several new python classes to easily manage, analyze and visualize orientational structural geology data.


You need Python 3.6 or later to run APSG. The package requires NumPy and SciPy, and the plotting routines require Matplotlib.

Quick start

APSG can be installed using pip:

pip install apsg

If you want tu run the latest version of code, you can install it from git:

pip install git+git://

Alternatively, you can download the package manually from the GitHub repository, unzip it, navigate into the package, and use the command:

python install

Upgrading via pip

To upgrade an existing version of APSG from PyPI, execute

pip install apsg --upgrade --no-deps

Please note that the dependencies (Matplotlib, NumPy and SciPy) will also be upgraded if you omit the --no-deps flag; use the --no-deps ("no dependencies") flag if you don't want this.

Installing APSG from the source distribution

In rare cases, users reported problems on certain systems with the default pip installation command, which installs APSG from the binary distribution ("wheels") on PyPI. If you should encounter similar problems, you could try to install APSG from the source distribution instead via

pip install --no-binary :all: apsg

Also, I would appreciate it if you could report any issues that occur when using pip install apsg in hope that we can fix these in future releases.


The APSG package is also available through conda-forge.

Current release info

Name Downloads Version Platforms
Conda Recipe Conda Downloads Conda Version Conda Platforms

Installing apsg

Installing apsg from the conda-forge channel can be achieved by adding conda-forge to your channels with:

conda config --add channels conda-forge

Once the conda-forge channel has been enabled, apsg can be installed with:

conda install apsg

It is possible to list all of the versions of apsg available on your platform with:

conda search apsg --channel conda-forge

Getting started

You can see APSG in action in accompanied Jupyter notebook

And for fun check how simply you can animate stereonets


Explore the full features of APSG. You can find detailed documentation here.


Most discussion happens on Github. Feel free to open an issue or comment on any open issue or pull request. Check for more details.


APSG is an open-source project, available for you for free. It took a lot of time and resources to build this software. If you find this software useful and want to support its future development please consider donating me.

Donate via PayPal


APSG is free software: you can redistribute it and/or modify it under the terms of the MIT License. A copy of this license is provided in LICENSE file.


0.7.0 (3 Feb 2021)

  • Python 2 support dropped
  • RosePlot added
  • Ortensor has from_pairs method for Lisle tensor for orthogonal data
  • StereoNet scatter method has labels kwarg to show hover annotations

0.6.3 (6 Dec 2019)

  • Python 2/3 compatibility fix

0.6.2 (6 Dec 2019)

  • few minor bugs fixed
  • Stereogrid apply_func passes Vec3 instead numpy array
  • Pair H method to get mutual rotation implemented
  • velgrad method of DefGrad accepts steps kwarg to generate list of DefGrad tensors
  • Added Tensor class to work with deformation tensors

0.6.1 (12 Dec 2018)

  • Stereogrid always use Euclidean norms as weights
  • DefGrad properties e1, e2, e3 (natural principal strains) added
  • DefGrad properties eoct, goct (octahedral strains) added
  • DefGrad from_ratios class method added
  • DefGrad properties k, d, K, D (strain symmetries and intesities) added
  • New class Ellipsoid added to work with ellipsoids
  • FabricPLot renamed to VollmerPlot for consistency
  • RamsayPlot, FlinnPlot and HsuPlot implemented
  • All fabric plots have new path method accepting list of tensors

0.6.0 (07 Nov 2018)

  • Stress always gives eigenvalues sorted
  • Stress I1, I2, I3 properties for invariants implemented
  • Stress mean_stress property implemented
  • Stress hydrostatic and deviatoric properties implemented
  • precision added to settings to control numerical comparisms
  • figsize added to settings to control figure size across APSG
  • Animation examples fixed
  • rand class method implemented for Fol, Lin, Vec3 and Pair to generate random instance
  • Group to_csv and from_csv improved
  • SDB tags method works properly for multiple tags
  • SDB can modify database metadata
  • QGIS 3 plugin ReadSDB compatibility

0.5.4 (19 Oct 2018)

  • StereoNet has cbpad keyword for colorbar padding
  • FabricPlot bug introduced in 0.5.2 fixed.

0.5.3 (10 Oct 2018)

  • Bugfix release

0.5.2 (10 Oct 2018)

  • Fischer distribution sampling added
  • transform method has norm kwarg to normalize tranformed vectors
  • axisangle property to calculate axis and angle from rotation matrix
  • StereoNet arc method added
  • Vec3 and Group upper and flip properties implemented
  • DefGrad, VelGrad and Stress rotate method accepts also rotation matrix
  • velgrad method added to DefGrad to calculate matrix logarithm
  • StereoGrid has new methods max, min, max_at, min_at

0.5.1 (05 Dec 2017)

  • Kent distribution sampling added
  • Automatic kernel density estimate for contouring
  • UserWarnings fix

0.5.0 (19 Nov 2017)

  • bux fix minor release

0.4.4 (25 Mar 2017)

  • Group method centered improved
  • Group method halfspace added to reorient all vectors towards resultant halfspace

0.4.3 (25 Mar 2017)

  • Stress tensor with few basic methods implemented
  • StereoGrid keyword argument 'weighted' to control weighting
  • StereoNet kwargs are passed to underlying methods for immediate plots
  • StereoNet tensor method implemented (draw eigenlins or fols based on fol_plot settings)
  • Group totvar property and dot and proj methods implemented
  • Fol and Lin dot method returns absolute value of dot product
  • Vec3 H method to get mutual rotation implemented
  • StereoNet.contourf method draw contour lines as well by default. Option clines controls it.
  • centered bug fixed
  • StereoNet allows simple animations. Add animate=True kwarg to plotting method and finally call StereoNet animate method.

0.4.1-2 (04 Mar 2017)

  • bugfix

0.4.0 (04 Mar 2017)

  • Density class renamed to StereoGrid
  • Fault sense under rotation fixed
  • FaultSet example provided
  • Angelier-Mechler dihedra method implemented for FaultSet
  • StereoNet accepts StereoGrid and Ortensor as quick plot arguments
  • StereoNet instance has axtitle method to put text below stereonet

0.3.7 (05 Jan 2017)

  • conda build for all platforms
  • numpy, matplotlib and other helpres imported by default
  • ortensor is normed by default
  • ortensor MADp, MADo, MAD and kind properties added

0.3.6 (03 Jan 2017)

  • shell script iapsg opens interactive console

0.3.5 (12 Nov 2016)

  • Simple settings interface implemented in in apsg.core.seetings dictionary. To change settings use:
    from apsg.core import settings
  • notation setting with values dd or rhr control how azimuth argument of Fol is represented.
  • vec2dd setting with values True or False control how Vec3 is represented.
  • Vec3 could be instantiated by one arument (vector like), 2 arguments (azimuth, inclination) or 3 arguments (azimuth, inclination, magnitude).
  • Group and FaultSet can return array or list of user-defined attributes of all elements

0.3.4 (20 Jun 2016)

  • RTD fix

0.3.3 (04 Jun 2016)

  • Added E1,E2,E3 properties and polar decomposition method to DefGrad object
  • StereoNet has vector method to mimics lower and upper hemisphere plotting of Lin and Vec3 objects as used in paleomagnetic plots
  • StereoNet could be initialized with subplots
  • rake method of Fol added to return vector defined by rake
  • Density could be initialized without data for user-defined calculations New method apply_func could be used to calculate density
  • Contour(f) methods accept Density object as argument
  • Added Group class methods to generate Spherical Fibonacci and Golden Section based uniform distributions of Vec3, Lin and Fol

0.3.2 (22 Feb 2016)

  • FabricPlot - triangular fabric plot added
  • .asvec3 property has .V alias
  • Resultant of Fol and Lin is calculated as vectorial in centered position
  • dv property of Fol added to return dip slip vector

0.3.1 (20 Nov 2015)

  • SDB class improved. Support basic filtering including tags
  • StereoNet has close method to close figure and new method to re-initialize figure when closed in interactive mode
  • iapsg shell script added to invoke apsg ipython shell

0.3.0 (09 Nov 2015)

  • Group fancy indexing implemented. Group could be indexed by sequences of indexes like list, tuple or array as well as sliced.
  • Cluster class with hierarchical clustering implemented
  • Group to_file and from_file methods implemented to store data in file
  • Group copy method for shallow copy implemented
  • StereoNet now accept Vec3 and Fault object as well for instant plotting.
  • Ortensor updated with new properties E1,E2,E3 and Vollmer(1989) indexes P,G,R and C. Bug in Woodcocks's shape and strength values fixed.
  • uniform_lin and uniform_fol improved.
  • asvec3 method implemented for Fol and Lin
  • fol_plot property of StereoNet allows choose poles or great circles for immediate plotting
  • bootstrap method of Group provide generator of random resampling with replacements.
  • Group examples method provide few well-known datasets.
  • Matplotlib deprecation warnings are ignored by default

0.2.3 (21 Oct 2015)

  • New Docstrings format
  • StereoNet.getfols method bug fixed.
  • Shell scripts to run interactive session improved.

0.2.2 (17 Apr 2015)

  • FaultSet class added. Fault and Hoeppner methods of StereoNet implemented
  • VelGrad and DefGrad classes used for transformations added
  • G class to quickly create groups from strings added.

0.2.1 (09 Dec 2014)

  • Quick plotting of groups fixed.

0.2.0 (09 Dec 2014)

  • new StereoNet class for Schmidt projection
  • Quick plot when data are passed as argument StereoNet class instantiation
  • mplstereonet dependency depreceated
  • new Pair and Fault classes to manipulate paired data (full support in future)
  • new uniform_lin and uniform_fol Group methods
  • abs for Group implemented to calculate euclidean norms
  • new Group method normalized
  • new Group properties and methods to calculate spherical statistics

0.1.0 (01 Nov 2014)

  • First release of APSG

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