Processing of logratio data. In each subfigure, rows corresponds to samples and columns to probes. On the left: the effect of rank transformation; the same fragment of the genome represented by logratios (a) and their column ranks (b). The wave pattern is eliminated, while true signal (clear deletion) is strengthen. On the right: the polymorphic region in the middle is surrounded by wave patterns and only one significant deletion is visible (c); markers found by our algorithm indicate only deleted segment, all other spurious signals are ignored (d).