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A package originally made for working with external and internal activities of ordered matroids in Macaulay2, it is the companion code to the article Internally Perfect Matroids. It now includes a number of methods for working with unordered matroids.


Version 0.2 of MatroidActivities greatly expands on Version 0.1. There are new methods for computing with both matroids and ordered matroids. The new functionality includes:

  • Methods for constructing a(n ordered) matroid from an ideal, simplicial complex, or central arrangement;
  • Methods for constructing the face ring, Chow ring, and Orlik-Solomon algebra of a matroid or ordered matroid;
  • Testing if a matroid is simple, binary, ternary, (co)graphic, regular, or paving;
  • TikZ rendering of the internal order and the external order split into two methods for improved visualization.


There are three resources for learning to use this package: the first two provided by the author and the third by the user.

Every method in the package is documented and an attempt was made to make this documentation reasonably thorough. You can access the documentation in Macaulay2 using the help and viewHelp commands.

Moreover, an introductory session is available as a guide to this package.

Finally, and probably most importantly, is the user's curiosity about, and need for, such software.


  • First you will need a working version of Macaulay2 (M2). Follow the instructions on the M2 homepage to download and install. The source code for M2 is available on GitHub here.

  • The MatroidActivities package builds on and extends J. Chen's Matroids package for M2. So for MatroidActivities to work you will need to have Matroids installed. You can get the source code for that package here. Then simply add it to /Macaulay2/code and enter the following into any M2 interactive shell:

    i1: installPackage "Matroids"

  • Finally add MatroidActivities.m2 to /Macaulay2/code and then run:

    i2: installPackage "MatroidActivities"

    i3: loadPackage "MatroidActivities"


A package for working with ordered matroids in Macaulay2




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