  In this paper, a modified factor $\mu$, which characterizes modified gravity
in the linear matter density perturbation theory, is reconstructed in a
data-driven and almost model-independent way via Gaussian process by using
currently available cosmic observations. Utilizing the Pantheon+ SNe Ia
samples, the observed Hubble parameter $H(z)$ and the redshift space distortion
$f\sigma_8(z)$ data points, one finds out a time varying $\mu$ at low
redshifts. The reconstructed $\mu$ implies that more complicated modified
gravity beyond the simplest general relativity and the Dvali-Gabadadze-Porrati
braneworld model is required.
