where β z adjusts the weight of the folder I based on the relative size of folder I ∈ T 0 z , and β t adjusts the weight based on the relative size of folder J ∈ T 0 t . These values should be set according to the smoothness of the data in the physical space and temporal axes, z and t, respectively. For smoother data, we would like to put more weights on larger folders to induce a coarser representation, and therefore larger values for the coefficients β z and β t . For more details on the relationship between smoothness and the ℓ 1 norm of F p (•) over X p , refer to .