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Approximate π (Pi) with Monte-Carlo method
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<iframe 
    src="http://jsxgraph.uni-bayreuth.de/share/iframe/approximate-pi-pi-with-monte-carlo-method" 
    style="border: 1px solid black; overflow: hidden; width: 550px; aspect-ratio: 55 / 65;" 
    name="JSXGraph example: Approximate π (Pi) with Monte-Carlo method" 
    allowfullscreen
></iframe>
This code has to 
<div id="board-0-wrapper" class="jxgbox-wrapper " style="width: 100%; ">
   <div id="board-0" class="jxgbox" style="aspect-ratio: 1 / 1; width: 100%;" data-ar="1 / 1"></div>
</div>


<div id="resulttext"></div>
<script type = "text/javascript"> 
    /*
    This example is licensed under a 
    Creative Commons Attribution ShareAlike 4.0 International License.
    https://creativecommons.org/licenses/by-sa/4.0/
    
    Please note you have to mention 
    The Center of Mobile Learning with Digital Technology
    in the credits.
    */
    
    const BOARDID = 'board-0';

    const board = JXG.JSXGraph.initBoard(BOARDID, {
        boundingbox: [-1, 1, 1, -1],
        axis: true,
        pan: { needTwoFingers: true }
    });
    
    var c, i, count = 0,
        tin = 0,
        tout = 0,
        p = [],
        updateText;
    var c = board.create('circle', [
        [0, 0], 1
    ]);
    
    p = [];
    for (var i = 0; i < 50; i++) {
        p[i] = board.create('point',
            [function() {
                return 2 * Math.random() - 1;
            }, function() {
                return 2 * Math.random() - 1;
            }], {
                name: ' ',
                withLabel: false
            });
    }
    
    updateText = function() {
        var i, inp, outp, x, y, text = '';
        count++;
    
        inp = 0;
        outp = 0;
    
        for (i = 0; i < p.length; i++) {
            x = p[i].X();
            y = p[i].Y();
    
            if (x * x + y * y <= 1) {
                inp++;
            } else {
                outp++;
            }
        }
        tin += inp;
        tout += outp;
    
        text += '<b>Current:</b><br />in: ' + inp + ', out: ' + outp + ', total: ' + (inp + outp) +
            '; ratio: ' + (inp / (inp + outp)) + ', ratio*4: ' + (4 * inp / (inp + outp)) +
            '.<br /><b>Total:</b> (' + count + ' updates in total)<br/>I´in: ' + tin + ', out: ' + tout +
            ', total: ' + (tin + tout) + '; <br />ratio: ' + (tin / (tin + tout)) + ', <br />ratio*4: ' + (4 * tin / (tin + tout));
    
        document.getElementById('resulttext').innerHTML = text;
    }
    
    board.on('update', updateText);
    
    JXG.addEvent(document.getElementById(BOARDID), 'mousemove', function() {
        this.update();
    }, board);
 </script> 
/*
This example is licensed under a 
Creative Commons Attribution ShareAlike 4.0 International License.
https://creativecommons.org/licenses/by-sa/4.0/

Please note you have to mention 
The Center of Mobile Learning with Digital Technology
in the credits.
*/

const BOARDID = 'your_div_id'; // Insert your id here!

const board = JXG.JSXGraph.initBoard(BOARDID, {
    boundingbox: [-1, 1, 1, -1],
    axis: true,
    pan: { needTwoFingers: true }
});

var c, i, count = 0,
    tin = 0,
    tout = 0,
    p = [],
    updateText;
var c = board.create('circle', [
    [0, 0], 1
]);

p = [];
for (var i = 0; i < 50; i++) {
    p[i] = board.create('point',
        [function() {
            return 2 * Math.random() - 1;
        }, function() {
            return 2 * Math.random() - 1;
        }], {
            name: ' ',
            withLabel: false
        });
}

updateText = function() {
    var i, inp, outp, x, y, text = '';
    count++;

    inp = 0;
    outp = 0;

    for (i = 0; i < p.length; i++) {
        x = p[i].X();
        y = p[i].Y();

        if (x * x + y * y <= 1) {
            inp++;
        } else {
            outp++;
        }
    }
    tin += inp;
    tout += outp;

    text += '<b>Current:</b><br />in: ' + inp + ', out: ' + outp + ', total: ' + (inp + outp) +
        '; ratio: ' + (inp / (inp + outp)) + ', ratio*4: ' + (4 * inp / (inp + outp)) +
        '.<br /><b>Total:</b> (' + count + ' updates in total)<br/>I´in: ' + tin + ', out: ' + tout +
        ', total: ' + (tin + tout) + '; <br />ratio: ' + (tin / (tin + tout)) + ', <br />ratio*4: ' + (4 * tin / (tin + tout));

    document.getElementById('resulttext').innerHTML = text;
}

board.on('update', updateText);

JXG.addEvent(document.getElementById(BOARDID), 'mousemove', function() {
    this.update();
}, board);
At construction time each point receives a function pair as coordinates. In each update, these functions (which call `Math.random()`) are called. Thus, in each update each point receives new random coordinates. The 50 points are updated on `move` events. This can be used to calculate $\pi$ using statistics. In each update we count the number of points inside the circle (with midpoint [0,0] and radius 1) and outside the circle. The points are restricted to the square with midpoint [0,0] and edges of length 2. We add a `mouseover` event listener to the JSXGraph to trigger the repositioning of the points on every mouse move. 
// Define the id of your board in BOARDID

const board = JXG.JSXGraph.initBoard(BOARDID, {
    boundingbox: [-1, 1, 1, -1],
    axis: true,
    pan: { needTwoFingers: true }
});

var c, i, count = 0,
    tin = 0,
    tout = 0,
    p = [],
    updateText;
var c = board.create('circle', [
    [0, 0], 1
]);

p = [];
for (var i = 0; i < 50; i++) {
    p[i] = board.create('point',
        [function() {
            return 2 * Math.random() - 1;
        }, function() {
            return 2 * Math.random() - 1;
        }], {
            name: ' ',
            withLabel: false
        });
}

updateText = function() {
    var i, inp, outp, x, y, text = '';
    count++;

    inp = 0;
    outp = 0;

    for (i = 0; i < p.length; i++) {
        x = p[i].X();
        y = p[i].Y();

        if (x * x + y * y <= 1) {
            inp++;
        } else {
            outp++;
        }
    }
    tin += inp;
    tout += outp;

    text += 'Current:
in: ' + inp + ', out: ' + outp + ', total: ' + (inp + outp) +
        '; ratio: ' + (inp / (inp + outp)) + ', ratio*4: ' + (4 * inp / (inp + outp)) +
        '.
Total: (' + count + ' updates in total)
I´in: ' + tin + ', out: ' + tout +
        ', total: ' + (tin + tout) + '; 
ratio: ' + (tin / (tin + tout)) + ', 
ratio*4: ' + (4 * tin / (tin + tout));

    document.getElementById('resulttext').innerHTML = text;
}

board.on('update', updateText);

JXG.addEvent(document.getElementById(BOARDID), 'mousemove', function() {
    this.update();
}, board);
<div id="resulttext"></div>

license

This example is licensed under a Creative Commons Attribution ShareAlike 4.0 International License.
Please note you have to mention The Center of Mobile Learning with Digital Technology in the credits.