Difference between revisions of "Polynomial regression I"

From JSXGraph Wiki
Jump to navigationJump to search
Line 9: Line 9:
 
     datax = [];
 
     datax = [];
 
     for (i = 0; i < data.length; i++)  {  
 
     for (i = 0; i < data.length; i++)  {  
         data[i] = (parseFloat(data[i])-450.0);  
+
         //data[i] = (parseFloat(data[i])-450.0);
 +
        data[i] = (parseFloat(data[i]));  
 
         datax[i] = i;
 
         datax[i] = i;
 
         }
 
         }
 
      
 
      
  
brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-2, 100, data.length+2, -70], grid: false, axis:true});
+
brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-2, 300, data.length+2, -70], grid: false, axis:true});
 
s = brd.createElement('slider',[[10,70],[80,70],[0,1,1]],{name:'scale'});     
 
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});     
 
deg = brd.createElement('slider',[[10,90],[80,90],[1,1,10]],{name:'degree',snapWidth:1});     

Revision as of 14:25, 3 August 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>