Spearman coefficients, ρ, between the infall time, t_fall, and the linear distance, d_linear, as functions of the slope, k. Solid and dashed curves show results in the R − V diagram and phase space, respectively. Black curves represent the full galaxy sample, with vertical lines marking the optimal k where ρ reaches minima. Blue and orange curves represent the low-mass and high-mass galaxies, respectively, with corresponding minima indicated by open circles.