Creating a polygon from an unordered set of points
One possibility: Estimate the center of the polygon with the mean of the x coords and the mean of the y coords. Calculate the angle of each point from that center point using the atan2 function sort the data by the angle calculated. This will not be perfect if you have inlets and peninsulas, but would at least get you started and those points could be adjusted by hand or by an algorithm that looks for crossings/self-intersections and reverses the order of the points that cause the cross.
On Tue, Oct 23, 2012 at 11:50 AM, peleve <pitiur at gmail.com> wrote:
Hello, I have the contour of the shoreline of a lake. I have measured data points away from the lake shore signifying a particular depth. The data is not ordered as a polygon and hence trying to draw it creates a series of lines all over the place. I would like to turn the points into a ordered set that results in a smooth polygon. I have tried a "nearest point" approach. An example is shown here: http://www.deepcreekanswers.com/samples/sampledata.png. I've tried a closest perpendicular distance to the shoreline polygon elements approach. But it's worse. Does anyone have an approach that might work? Thank you a priori. Pete Versteegen -- View this message in context: http://r.789695.n4.nabble.com/Creating-a-polygon-from-an-unordered-set-of-points-tp4647181.html Sent from the R help mailing list archive at Nabble.com.
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Gregory (Greg) L. Snow Ph.D. 538280 at gmail.com