Difference between revisions of "Polynomial regression I"

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Line 18: Line 18:
 
var deg = brd.create('slider',[[10,90],[80,90],[1,1,10]],{name:'degree',snapWidth:1});     
 
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});   
+
var curve = brd.create('curve',[[],[]],{strokeColor:'gray',strokeWidth:3, dash:2});   
 
curve.updateDataArray = function() {
 
curve.updateDataArray = function() {
 
     var i, len = data.length;
 
     var i, len = data.length;
Line 29: Line 29:
  
 
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:'blue', strokeWidth:3});     
 
brd.create('glider',[100,30,reg],{strokeColor:'black'});     
 
brd.create('glider',[100,30,reg],{strokeColor:'black'});     
  

Revision as of 18:02, 21 November 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]; 
}
curve.update(); // Needed for correct glider position

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:18});     
brd.unsuspendUpdate();