  We propose a method to calculate the charge dynamical structure factors for
the ground states of correlated electron systems based on the variational Monte
Carlo method. Our benchmarks for the one- and two-dimensional Hubbard models
show that inclusion of composite-fermion excitations in the basis set greatly
improves the accuracy, in reference to the exact charge dynamical structure
factors for clusters. Together with examination for larger systems beyond
tractable sizes by the exact diagonalization, our results indicate that the
variational Monte Carlo method is a promising way for studies on the nature of
charge dynamics in correlated materials such as the copper oxide
superconductors, if the composite-fermion excitations are properly included in
the restricted Hilbert space of intermediate states in the linear response
theory. Our results are consistent with the particle-hole excitations inferred
from the single-particle spectral function $A(\mathbf{k}, \omega)$ in the
literature. We also discuss the importance of incorporating nonlocal composite
fermion for more accurate description. Future issues for further improvements
are also discussed.
