  Detailed dynamical systems models used in life sciences may include dozens or
even hundreds of state variables. Models of large dimension are not only harder
from the numerical perspective (e.g., for parameter estimation or simulation),
but it is also becoming challenging to derive mechanistic insights from such
models. Exact model reduction is a way to address this issue by finding a
self-consistent lower-dimensional projection of the corresponding dynamical
system. A recent algorithm CLUE allows one to construct an exact linear
reduction of the smallest possible dimension such that the fixed variables of
interest are preserved. However, CLUE is restricted to systems with polynomial
dynamics. Since rational dynamics occurs frequently in the life sciences (e.g.,
Michaelis-Menten or Hill kinetics), it is desirable to extend CLUE to the
models with rational dynamics. In this paper, we present an extension of CLUE
to the case of rational dynamics and demonstrate its applicability on examples
from literature. Our implementation is available in version 1.5 of CLUE at
https://github.com/pogudingleb/CLUE.
