  Matroidal entropy functions are entropy functions in the form $\mathbf{h} =
\log v \cdot \mathbf{r}_M$ , where $v \ge 2$ is an integer and $\mathbf{r}_M$
is the rank function of a matroid $M$. They can be applied into capacity
characterization and code construction of information theory problems such as
network coding, secret sharing, index coding and locally repairable code. In
this paper, by constructing the variable strength arrays of some matroid
operations, we characterized matroidal entropy functions induced by regular
matroids and some matroids with the same p-characteristic set as uniform
matroid $U_{2,4}$.
