Interpolation: Neville's algorithm
From JSXGraph Wiki
References
The underlying JavaScript code
board = JXG.JSXGraph.initBoard('box', {axis:true, boundingbox: [-5, 5, 7, -3]});
board.suspendUpdate();
var p = [];
p[0] = board.create('point', [-1,2], {size:4});
p[1] = board.create('point', [3,-1], {size:4});
p[2] = board.create('point', [2,1], {size:4});
var graph = board.create('curve', JXG.Math.Numerics.Neville(p),{strokeWidth:5,strokeOpacity:0.5});
g = board.create('glider', [graph]);
t = board.create('tangent', [g],{dash:1,strokeColor:'green'});
board.unsuspendUpdate();
function addPoint() {
p.push(board.create('point',[(Math.random()-0.5)*10,(Math.random()-0.5)*3],{size:4}));
board.update();
}