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convex_hull Scilab Group Scilab function convex_hull
NAME
convex_hull - convex hull of a set of points in the plane
CALLING SEQUENCE
[nhull,ind] = convex_hull(xy)
PARAMETERS
xy : 2 x n real matrix
nhull
: integer
ind : integer row vector
DESCRIPTION
convex_hull finds the convex hull of a given set of n points in the
plane. xy is the 2 x n matrix of the (x,y) coordinates of the given
points. convex_hull returns in nhull the number of the points of the
boundary of the convex hull and in ind the row vector (of size nhull)
giving the indices in xy of the points of the boundary. The order in ind
corresponds to consecutive points on the boundary.
EXAMPLE
ta=[27 27 3 12 11 12 27 26 26 25 25 24 23 23 21 22 21 20 19 18 18];
ta=[ta 16 15 15 14 12 9 10 6 9 17 8 17 10 20 11 23 23 12 18 28];
he=[ 1 2 2 4 5 11 13 1 25 22 24 22 22 19 13 13 14 16 16 9 16];
he=[he 10 10 11 12 2 6 5 5 7 8 7 9 6 11 4 18 13 3 28 17];
g=make_graph('foo',0,28,ta,he);
xx=[46 120 207 286 366 453 543 544 473 387 300 206 136 250 346 408];
g('node_x')=[xx 527 443 306 326 196 139 264 55 58 46 118 513];
yy=[36 34 37 40 38 40 35 102 102 98 93 96 167 172 101 179];
g('node_y')=[yy 198 252 183 148 172 256 259 258 167 109 104 253];
show_graph(g);
xy=[g('node_x');g('node_y')];
[nhull,ind] = convex_hull(xy)
show_nodes(ind);
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