Hulls, masks, and smoothing

• A cluster of 2D points can be replaced by its bounding polygon using the new filter convexhull. A path-smoothed bounding curve can be plotted as a filled area using "convexhull smooth path with filledcurves". See convexhull.
• An alternative filter concavehull generates a bounding polygon that is not necessarily convex; instead it forms a χ-shape determined by a characteristic length parameter that controls the degree of concavity. This essentially draws a blob around the data points. See concavehull.
• A convex hull or other polygon can be used as a mask to display only selected portions of a pm3d surface or an image plot. See new plot style with mask (defines a mask) and keyword mask (applies the mask to a subsequent plot component).
• curve smoothing using along-path cubic splines suitable for closed curves or for 2D curves that are not monotonic on x. See smooth path. This allows smoothing of hulls and masks.
• cubic spline smoothing of 3D lines. See splot smooth csplines
• Smoothing options apply to plotting with filledcurves {above|below|between}.
• New keyword period for smoothing periodic data. See smooth kdensity.