Difference between revisions of "Polynomial regression I"

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Line 29: Line 29:
 
             function(){ return "r(x) = " + regressionPolynomial.getTerm();}
 
             function(){ return "r(x) = " + regressionPolynomial.getTerm();}
 
             ],
 
             ],
             {strokeColor:'black',fontSize:'14px'});     
+
             {strokeColor:'black',fontSize:14});     
 
brd.unsuspendUpdate();
 
brd.unsuspendUpdate();
 +
brd.update();
 
</jsxgraph>
 
</jsxgraph>
  

Revision as of 11:12, 7 August 2013

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

var data = "406.60 428.50 429.30 426.30 434.70 415.90 ... many points ... 521.80 524.40 526.80";
data = data.split(' ');
var datax = [];
for (i = 0; i < data.length; i++)  { 
    data[i] = (parseFloat(data[i])-450.0); 
    datax[i] = i;
}
    
var brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-2, 100, data.length+2, -70], grid: false, axis:true});
brd.suspendUpdate();
var s = brd.create('slider',[[10,70],[80,70],[0,1,1]],{name:'scale'});     
var deg = brd.create('slider',[[10,90],[80,90],[1,1,10]],{name:'degree',snapWidth:1});     
var curve = brd.create('curve',[[],[]],{strokeColor:'gray',dash:2});     
curve.updateDataArray = function() {
    var i, len = data.length;
    this.dataX = datax.slice(0,len); 
    for(i=0;i<len;i++) this.dataY[i] = s.Value()*data[i]; 
}
var regressionPolynomial = JXG.Math.Numerics.regressionPolynomial(deg,datax,curve.dataY);

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

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