15.5.361 lsmooth

lsmooth(image, vx, vy [, /boxcar, /gaussian, /onesided, /twosided, /normalize])

Returns a directionally smoothed version of image. vx and vy contain the two coordinates of the direction at each point. The direction of the stream vector is the direction of the streamline through the 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. For each point, its data value is spread across data points on 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 target 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 target interval extends in both directions from the starting point (determined by the direction of the stream vector and the exactly opposite direction).

By default (or if /boxcar is specified), the spreading 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 spreading is gaussian instead, with the length of the stream vector indicating the FWHM of the gaussian kernel.

By default, a value that is spread to a particular data element is multiplied by the length of the segment of the streamline or straight line that falls within the data element, and by a gaussian weight (if /gaussian was selected), but is not normalized to take into account the smoothing width. If /normalize is specified, then the spread values are normalized with the smoothing width, too, so that the total of the smoothed data equals the total of the unsmoothed data (except for edge effects).

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: dsmooth, esmooth, gsmooth, smooth