Difference between revisions of "Polynomial regression I"

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Line 20: Line 20:
 
     for(i=0;i<len;i++) this.dataY[i] = s.Value()*data[i];  
 
     for(i=0;i<len;i++) this.dataY[i] = s.Value()*data[i];  
 
}
 
}
brd.update();
+
//brd.update();
 
var regressionPolynomial = JXG.Math.Numerics.regressionPolynomial(deg,datax,curve.dataY);
 
var regressionPolynomial = JXG.Math.Numerics.regressionPolynomial(deg,datax,curve.dataY);
  
 
var reg = brd.create('functiongraph',[regressionPolynomial],{strokeColor:'black'});     
 
var reg = brd.create('functiongraph',[regressionPolynomial],{strokeColor:'black'});     
 +
/*
 
brd.create('glider',[100,30,reg],{strokeColor:'black'});     
 
brd.create('glider',[100,30,reg],{strokeColor:'black'});     
  
Line 30: Line 31:
 
             ],
 
             ],
 
             {strokeColor:'black',fontSize:'14px'});     
 
             {strokeColor:'black',fontSize:'14px'});     
 +
*/
 
</jsxgraph>
 
</jsxgraph>
  

Revision as of 23:34, 8 September 2010

Through the points defining the dashed line the regression polynomial of degree 'degree' is computed and displayed. The points can be scaled by adjusting the slider 'scale'. The degree of the regression polynomial can be changed by using the slider 'degree'.

The underlying JavaScript code

<jsxgraph width="700" height="500">

    data = "406.60 428.50 429.30 426.30 434.70 415.90 ... many points ... 521.80 524.40 526.80";
    data = data.split(' ');
    datax = [];
    for (i = 0; i < data.length; i++)  { 
        data[i] = (parseFloat(data[i])-450.0); 
        datax[i] = i;
        }
    

brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-2, 100, data.length+2, -70], grid: false, axis:true});
s = brd.createElement('slider',[[10,70],[80,70],[0,1,1]],{name:'scale'});     
deg = brd.createElement('slider',[[10,90],[80,90],[1,1,10]],{name:'degree',snapWidth:1});     
curve = brd.createElement('curve',[datax,[]],{strokeColor:'gray',dash:2});     
curve.updateDataArray = function() {
    var i, len = data.length;
    for(i=0;i<len;i++) { this.dataY[i] = s.Value()*data[i]; }
}
regressionPolynomial = JXG.Math.Numerics.regressionPolynomial(deg,datax,curve.dataY);  // generateFunction();

reg = brd.createElement('functiongraph',[regressionPolynomial],{strokeColor:'black'});     
brd.createElement('glider',[100,30,reg],{strokeColor:'black'});     

t = brd.createElement('text',[20,40,
            function(){ return "r(x) = " + regressionPolynomial.getTerm();}
            ],
            {strokeColor:'black',fontSize:'14px'});     

</jsxgraph>