Difference between revisions of "Analyze data with the Statistics software R"

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Line 19: Line 19:
 
<script language="JavaScript">
 
<script language="JavaScript">
 
         brd = JXG.JSXGraph.initBoard('jxgbox', {originX: 20, originY: 300, unitX: 60, unitY: 5});
 
         brd = JXG.JSXGraph.initBoard('jxgbox', {originX: 20, originY: 300, unitX: 60, unitY: 5});
 +
        brd.suspendUpdate();
 
         b1axisx = brd.createElement('axis', [[0,0], [1,0]], {ticksDelta:5, strokeColor:'#000000'});
 
         b1axisx = brd.createElement('axis', [[0,0], [1,0]], {ticksDelta:5, strokeColor:'#000000'});
 
         b1axisy = brd.createElement('axis', [[0,0], [0,1]], {ticksDelta:5, strokeColor:'#000000'});
 
         b1axisy = brd.createElement('axis', [[0,0], [0,1]], {ticksDelta:5, strokeColor:'#000000'});
Line 78: Line 79:
 
         p[8] = brd.createElement('glider', [x[8],y[8],l[2]],{name:' ',style:6});  
 
         p[8] = brd.createElement('glider', [x[8],y[8],l[2]],{name:' ',style:6});  
 
         p[9] = brd.createElement('glider', [x[9],y[9],l[3]],{name:' ',style:6});  
 
         p[9] = brd.createElement('glider', [x[9],y[9],l[3]],{name:' ',style:6});  
 +
        brd.unsuspendUpdate();
  
 
         doIt();
 
         doIt();
Line 142: Line 144:
 
</html>
 
</html>
  
=== The JavaScript code of the client: ===
+
=== The underlying source code ===
<source lang="javascript">
+
[[The JavaScript and PHP code of the client]]
        brd = JXG.JSXGraph.initBoard('jxgbox', {originX: 20, originY: 300, unitX: 60, unitY: 5});
 
        b1axisx = brd.createElement('axis', [[0,0], [1,0]], {ticksDelta:5, strokeColor:'#000000'});
 
        b1axisy = brd.createElement('axis', [[0,0], [0,1]], {ticksDelta:5, strokeColor:'#000000'});
 
        b1axisx.ticksDelta = 5;
 
        b1axisy.ticksDelta = 5;
 
        brd.fullUpdate = true;
 
        brd.update();
 
        brd.fullUpdate = false;
 
       
 
        var graph1,graph2,graph3,graph4,graph5,graph6,graph7,graph8,graph9;
 
 
 
        var x = [];
 
        var y = [];
 
        var p = [];
 
        var r1,r2,rad,phi,z1,z2;
 
        for (var i=0;i<6;i++) {
 
            x[i] = i;
 
            // Box-Muller-Method for standard normal random numbers
 
            r1 = Math.random();
 
            r2 = Math.random();
 
            rad = Math.sqrt(-2*Math.log(1-r1));
 
            phi = 2*Math.PI*r2;
 
            z1 = rad*Math.cos(phi);
 
            z2 = rad*Math.sin(phi);
 
            if(i < 5){
 
                y[i] = 10+z1*3;
 
                y[6+i] = 10+z2*3;
 
                x[6+i] = 6+i;
 
                p[i] = brd.createElement('point', [x[i],y[i]],{name:' ',fixed:true,style:7});
 
                p[6+i] = brd.createElement('point', [x[6+i],y[6+i]],{name:' ',fixed:true,style:7});
 
            }else{
 
                y[i] = 10+z1*3;
 
                p[i] = brd.createElement('point', [x[i],y[i]],{name:' ',fixed:true,style:7});
 
            }
 
        }
 
        var hlow = [];
 
        var hup = [];
 
        var l = [];
 
        hlow[0] = brd.createElement('point', [x[0],0],{name:' ',visible:false});
 
        hlow[1] = brd.createElement('point', [x[10],0],{name:' ',visible:false});
 
        hlow[2] = brd.createElement('point', [x[8],0],{name:' ',visible:false});
 
        hlow[3] = brd.createElement('point', [x[9],0],{name:' ',visible:false});
 
        hup[0] = brd.createElement('point', [x[0],20],{name:' ',visible:false});
 
        hup[1] = brd.createElement('point', [x[10],20],{name:' ',visible:false});
 
        hup[2] = brd.createElement('point', [x[8],20],{name:' ',visible:false});
 
        hup[3] = brd.createElement('point', [x[9],20],{name:' ',visible:false});
 
        l[0] = brd.createElement('line', [hlow[0],hup[0]],{visible:false});
 
        l[1] = brd.createElement('line', [hlow[1],hup[1]],{visible:false});
 
        l[2] = brd.createElement('line', [hlow[2],hup[2]],{visible:false});
 
        l[3] = brd.createElement('line', [hlow[3],hup[3]],{visible:false});
 
 
 
        brd.removeObject(p[0]);
 
        brd.removeObject(p[10]);
 
        brd.removeObject(p[8]);
 
        brd.removeObject(p[9]);
 
       
 
        p[0] = brd.createElement('glider', [x[0],y[0],l[0]],{name:' ',style:6});
 
        p[10] = brd.createElement('glider', [x[10],y[10],l[1]],{name:' ',style:6});
 
        p[8] = brd.createElement('glider', [x[8],y[8],l[2]],{name:' ',style:6});
 
        p[9] = brd.createElement('glider', [x[9],y[9],l[3]],{name:' ',style:6});
 
 
 
        doIt();
 
       
 
        function doIt() {
 
            brd.update();
 
            // Generate a ";"-separated list
 
            var t = '';
 
            for (var i=0;i<p.length;i++) {
 
                t += p[i].Y() + ';';
 
            }
 
            new Ajax.Request('/~alfred/jsxgraph/branches/0.70/examples/rserv.php', {
 
                method:'post',
 
                parameters:'input='+escape(t),
 
                onComplete: function(transport) {
 
                    if (200 == transport.status) {
 
                        var t = transport.responseText;
 
                        var res = t.match(/"(.*)"/gi);
 
                        res = RegExp.$1;
 
                        var a = res.split(";");
 
                        var m = a[0]*1.0;
 
                        var sd = a[1]*1.0;
 
                        var med = a[2]*1.0;
 
                        var mad = a[3]*1.0;
 
                        var mad = a[3]*1.0;
 
                        var est1 = a[4]*1.0;
 
                        var est2 = a[5]*1.0;
 
                        if (!graph2) {
 
                            graph2 = brd.createElement('curve', [[x[0],x[x.length-1]],[m,m]], {strokecolor:'red'});
 
                            graph3 = brd.createElement('curve', [[x[0],x[x.length-1]],[m+sd,m+sd]], {strokecolor:'red',dash:2});
 
                            graph4 = brd.createElement('curve', [[x[0],x[x.length-1]],[m-sd,m-sd]], {strokecolor:'red',dash:2});
 
                            graph5 = brd.createElement('curve', [[x[0],x[x.length-1]],[med,med]], {strokecolor:'gray'});
 
                            graph1 = brd.createElement('curve', [[x[0],x[x.length-1]],[med-mad,med-mad]], {strokecolor:'black',dash:3});
 
                            graph6 = brd.createElement('curve', [[x[0],x[x.length-1]],[med+mad,med+mad]], {strokecolor:'black',dash:3});
 
                            graph8 = brd.createElement('curve', [[x[0],x[x.length-1]],[est1,est1]], {strokecolor:'green'});
 
                            graph7 = brd.createElement('curve', [[x[0],x[x.length-1]],[est1-est2,est1-est2]], {strokecolor:'green',dash:4});
 
                            graph9 = brd.createElement('curve', [[x[0],x[x.length-1]],[est1+est2,est1+est2]], {strokecolor:'green',dash:4});
 
                        } else {
 
                            graph2.dataY = [m,m];
 
                            graph3.dataY = [m+sd,m+sd];
 
                            graph4.dataY = [m-sd,m-sd];
 
                            graph5.dataY = [med,med];
 
                            graph1.dataY = [med-mad,med-mad];
 
                            graph6.dataY = [med+mad,med+mad];
 
                            graph8.dataY = [est1,est1];
 
                            graph7.dataY = [est1-est2,est1-est2];
 
                            graph9.dataY = [est1+est2,est1+est2];
 
                        }
 
 
 
                        $('output').innerHTML = '<b><font size="+1">Normal location and scale:</font></b><br /><br />'+
 
                                '<b>Estimates for location (true value = 10):</b><br />' +
 
                                'Mean = ' + brd.round(m,2) + '<br />' +
 
                                'Median = ' + brd.round(med,2) + '<br />' +
 
                                'Radius-minimax estimator = ' + brd.round(est1,2) + '<br /><br />' +
 
                                '<b>Estimates for scale (true value = 3):</b><br />' +
 
                                'Standard deviation = ' + brd.round(sd,2) + '<br />' +
 
                                'MAD = ' + brd.round(mad,2) + '<br />' +
 
                                'Radius-minimax estimator = ' + brd.round(est2,2) + '<br />';
 
                        brd.update();
 
                    };
 
                }});
 
        }
 
</source>
 
  
=== The PHP code of the server (rserv.php) ===
 
<source lang="php">
 
<?php
 
$input = $_POST["input"];
 
if (!get_magic_quotes_gpc()) {
 
    $input = addslashes($input);
 
}
 
$cmd = "/usr/bin/Rscript LokSkala.R '" . $input ."'";
 
passthru($cmd);
 
?>
 
</source>
 
 
The R script can be [http://jsxgraph.uni-bayreuth.de/~alfred/jsxgraph/branches/0.70/examples/LokSkala.R downloaded here].
 
The R script can be [http://jsxgraph.uni-bayreuth.de/~alfred/jsxgraph/branches/0.70/examples/LokSkala.R downloaded here].
  

Revision as of 13:52, 11 December 2008

Normal Location and Scale

This litte application sends the y-coordinates of the points which are normal distributed (pseudo-)random numbers to the server.
There, location and scale of the sample are estimated using the Statistics software R.
The return values are plotted and displayed.

The computed estimates are:

  • mean, standard deviation: red (non-robust!)
  • median and MAD: black (most-robust!)
  • optimally robust radius-minimax estimator: green (cf. Rieder et al. (2008))

By changing the y-position of the four movable points you should recognize the instability (non-robustness) of mean and standard deviation in contrast to the robust estimates; e.g., move one of the four movable points to the top of the plot.

Online results:

Statistics:<br>

The underlying source code

The JavaScript and PHP code of the client

The R script can be downloaded here.

References

  • The Costs of not Knowing the Radius, Helmut Rieder, Matthias Kohl and Peter Ruckdeschel, Statistical Methods and Application 2008 Feb; 17(1): p.13-40; cf. also [1] for an extended version.
  • Robust Asymptotic Statistics, Helmut Rieder, Springer, 1994.
  • Numerical Contributions to the Asymptotic Theory of Robustness, Matthias Kohl, PhD-Thesis, University of Bayreuth, 2005; cf. also [2].

External links