  The chameleon model is a modified gravity theory that introduces an
additional scalar field that couples to matter through a conformal coupling.
This `chameleon field' possesses a screening mechanism through a nonlinear
self-interaction term which allows the field to affect cosmological observables
in diffuse environments whilst still being consistent with current local
experimental constraints. Due to the self-interaction term the equations of
motion of the field are nonlinear and therefore difficult to solve
analytically. The analytic solutions that do exist in the literature are either
approximate solutions and or only apply to highly symmetric systems. In this
work we introduce the software package SELCIE
(https://github.com/C-Briddon/SELCIE.git). This package equips the user with
tools to construct an arbitrary system of mass distributions and then to
calculate the corresponding solution to the chameleon field equation. It
accomplishes this by using the finite element method and either the Picard or
Newton nonlinear solving methods. We compared the results produced by SELCIE
with analytic results from the literature including discrete and continuous
density distributions. We found strong (sub-percentage) agreement between the
solutions calculated by SELCIE and the analytic solutions.
