Thank you for your answers, The answer is obviously not a convex hull since the shape of hysteresis loops is not convex. Currently, it seems to me that the best proposal is to use some known formula for the hysteresis loop and treat the problem as a curve fitting exercise. I now realize that the original problem is not simple. It is called "polygonization". There are actually some algorithms in the literature to solve this problem for special cases but not a general solution. For n points there are n! possibilities of ordering them. It is really a mess to sort out of this huge number the arrangements that result in a simple polygon and choose a particular "best polygon" out of this. But this is too much for me. I will try the curve fitting approach. Perhaps someone else is interested in solving the original problem. It is still interesting.
Regards, Eli On Thu, Feb 4, 2010 at 10:31 AM, Eli Brosh <[email protected]> wrote: > Hello, > I have an interesting problem and I hope it is possible to solve it using > sage. > I have a scanned digitized graph of a magnetic hysteresis loop. > That is, I have a list of points [(H0,B0),(H1,B1)....(Hn,Bn)] > however, the points are not ordered in any meaningful way. > In order to calculate the hysteresis loss, which is the area enclosed by > the loop, I need to somehow convert the list of points into a polyngon > (clockwise or counterclockwise). > I am not sure about the definition of this polygon. > Perhaps it is a simple polygon (not intersecting) which includes all the > points in the list as vertices and encloses the maximum area. > > Is there some algorithm that does it ? > Is there such a thing in sage ? > > Thanks, > Eli > -- To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
