15.5.145 dsmooth

dsmooth(image, vx, vy [, /boxcar, /gaussian, /onesided, /twosided, /total, /straight])

Returns a directionally smoothed version of image. vx and vy contain the two coordinates of the stream vector at each point. The direction of the stream vector is the direction of the streamline through the point. For each point, a weighted average or total is returned of data points on the streamline through that point, or, if /straight is specified, a weighted average or total of data points on the straight line which is tangential to the streamline through that point. The smoothing width is taken from the length of the stream vector.

By default, or if /onesided is selected, then the smoothing interval extends, for each point, to only one side of that point (determined by the direction of the stream vector). If /twosided is selected, then the smoothing interval extends in both directions from the starting point (determined by the direction of the stream vector and the exactly opposite direction).

Only the smoothing width at the point for which the weighted average is determined matters to the result at that point. By default (or if /boxcar is specified), the smoothing is of the boxcar type, and the total length of the boxcar is equal to the length of the stream vector (if /twosided is specified or implied), or to one half of the length of the stream vector (if /onesided is specified). If /gaussian is specified, then the smoothing is gaussian instead, with the length of the stream vector indicating the FWHM of the gaussian kernel.

By default, weighted averages are returned. If /total is specified, then weighted totals are returned instead.

lsmooth is very similar to dsmooth, except that in lsmooth a particular source value is spread along its associated streamline (or tangent), whereas in dsmooth a particular target value is constructed from source values taken from its associated streamline (or tangent).

See also: esmooth, gsmooth, lsmooth, smooth