*To*: mathgroup@smc.vnet.net*Subject*: [mg10803] set manipulation*From*: saha@rulgm0.LeidenUniv.nl (Nilay Saha)*Date*: Thu, 5 Feb 1998 00:58:48 -0500

Hello everyone, I have a problem with data set manipulation. I have a data set; data2D={{1.3,2.4},{1.4,5.6},{ ,},{ ,} }} <<DiscreteMath`ComputationalGeometry` delval=DelaunayTriangulation. The set delval gives the nearest neighbour of each of the data2D points.Thus delval may look like: delval={{1,{2,5,6}}, {2,{3,6,4}}, {3,{2,4 1}}, }} In the set delval 1=ist point in data2D (i.e in above eg. {1.3,2.4}) 2=2nd point 3=3rd Point and so on. Thus 1st point has it's nearest neighbour as 2nd, 5th, 6th points. Now I have to calculate the angle of the lines joining point 1 with it's nearest neighbour, with the x-axis=> angle=TanInverse[y(2)-y(1)/(x(2)-x(1))], where for sake of explanation point1={x(1),y(1)}, point2={x(2),y(2)} and so on for points 5,6. This should be done for all the points of data2D. Then I need to add the angles corresponding to each point and then find the average . So If anyone who could give a slight hint of how this sort of data manipulation can be done , I would be extremely grateful , Thnking you, Yours Sincerely, Nilay Saha Kamerlingh Onnes Lab, 2300RA Leiden Postbus: 9506, The Netherlands. Phone: (0031)71 5275476.