Figure 1: IIR filters applied to a waveform
The filters are causal, 3-ole Butterworth filters with corners as given in the plot labels. The routines used for the filtering have been possible in SAC for more than 20 years, but the fonts in the figures are true Postscript fonts, a feature added to SAC in v 101.5. The commands for producing this figure are in sac/macros/demo/filter.