# Lagrange interpolation

From JSXGraph Wiki

Revision as of 10:05, 8 June 2011 by Michael (talk | contribs) (moved Lagrange interpolation II to Lagrange interpolation)

Constructs a polynomial of degree [math]n[/math] through [math]n+1[/math] given points. Points can be added by clicking on "Add point". The dotted line is the graph of the first derivative, the dashed line is the graph of the second derivative.

### References

### The underlying JavaScript code

```
<link rel="stylesheet" type="text/css" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css" />
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
<div id="box" class="jxgbox" style="width:600px; height:400px;"></div>
```

```
board = JXG.JSXGraph.initBoard('box', {originX: 250, originY: 250, unitX: 50, unitY: 25});
// Axes
b1axisx = board.create('axis', [[0,0], [1,0]], {});
b1axisy = board.create'axis', [[0,0], [0,1]], {});
var p = [];
p[0] = board.create('point', [-1,2], {style:6});
p[1] = board.create('point', [3,-1], {style:6});
var f = board.lagrangePolynomial(p);
graph = board.create('functiongraph', [f, -10, 10], {strokeWidth:3});
d1 = board.create('functiongraph', [board.D(f), -10, 10], {dash:1});
d2 = board.create('functiongraph', [board.D(board.D(f)), -10, 10], {dash:2});
function addPoint() {
p.push(board.create('point',[(Math.random()-0.5)*10,(Math.random()-0.5)*3],{style:6}));
board.update();
}
```