build a new smoother nim from the nim argument. The result is build by replacing every image y0 of a breakpoint (x0, y0) by the minimum value of the y in a sequence of 2n + 1 breakpoints centered on (x0, y0). The first n breakpoints and the last n breakpoints are leaved untouched. The resulting nim has the same number of breakpoint as the argument with the same x.

See also @filter_max_t, @filter_median_t, @window_filter_t.