FILTER FILTER is a logical variable or real number which controls the filtering of data in order to eliminate plotting of overlapping data. If FILTER is YES, the data will be filtered. If FILTER is NO, 0, or blank, all data will be plotted. If FILTER is set to a real number, the default filter will be scaled by that number. FILTER = 1 corresponds to FILTER = YES. 0 < FILTER < 1 allows some data overlap. FILTER > 1 causes data to be more widely spaced.