B-splines

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The points are connected by a cubic B-spline curve (i.e. order=4).

The underlying JavaScript code

var brd = JXG.JSXGraph.initBoard('jxgbox',{boundingbox:[-4,4,4,-4],keepaspectratio:true,axis:true});
 
var p = [], col = 'red';
p.push(brd.create('point',[2,1],{strokeColor:col,fillColor:col}));
p.push(brd.create('point',[0.75,2.5],{strokeColor:col,fillColor:col}));
p.push(brd.create('point',[-0.3,0.3],{strokeColor:col,fillColor:col}));
p.push(brd.create('point',[-3,1],{strokeColor:col,fillColor:col}));
p.push(brd.create('point',[-0.75,-2.5],{strokeColor:col,fillColor:col}));
p.push(brd.create('point',[1.5,-2.8],{strokeColor:col,fillColor:col}));
p.push(brd.create('point',[2,-0.5],{strokeColor:col,fillColor:col}));
 
var c = brd.create('curve', JXG.Math.Numerics.bspline(p,4),
{strokecolor:'blue', strokeOpacity:0.6, strokeWidth:5});
 
var addSegment = function() {
brd.suspendUpdate();
p.push(brd.create('point',[Math.random()*8-4,Math.random()*8-4],
{strokeColor:col,fillColor:col}));
brd.unsuspendUpdate();
};
 
var removeSegment = function() {
brd.suspendUpdate();
 
if (p.length>2) {
brd.removeObject(p[p.length-1]); // remove the last point from the list of objects
p.splice(p.length-1,1); // remove the last point from the point array.
}
brd.unsuspendUpdate();
};
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