This function is provided by the package Matroids.
The truncation of a matroid M is the matroid T(M) on the same ground set as M whose rank function is given by taking the maximum of the rank of a set in M and the rank of M minus one. The truncation T(M) is an example of an elementary quotient of M. For a uniform matroid U_{r,n}, the truncation is just U_{r1,n}.



The flats of the truncation T(M) are just the flats of M with the hyperplanes removed.



The ifold truncation T^i(M) can be constructed as follows.


We can also construct the principal truncation of M with respect to some flat F. The principal truncation of M with respect to F is the elementary quotient of M corresponding to the principal modular cut associated to F.


