The effect of low-wavelength cut-off on performance accuracy. The ζ parameter was calculated for the SIMPLS algorithm using various low wavelength cut-offs applied to the SP175 dataset. In shades of red are the performance curves for α-helices (H) and in shades of blue are those for β-sheets (E). The thick solid lines indicate the performance using k = 8 (ie. 8 principal components). The thin lines are derived using progressively smaller values of k. The dashed lines are for values calculated using SELMAT3 instead of SIMPLS.