Difference between revisions of "Polynomial regression I"

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Line 26: Line 26:
 
     }
 
     }
 
}
 
}
curve.update();
+
curve.update(); // Needed for correct glider position
  
 
var regressionPolynomial = JXG.Math.Numerics.regressionPolynomial(deg, datax, curve.dataY);
 
var regressionPolynomial = JXG.Math.Numerics.regressionPolynomial(deg, datax, curve.dataY);
Line 60: Line 60:
 
     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];  
 
}
 
}
 +
curve.update(); // Needed for correct glider position
 +
 
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'});     

Revision as of 11:48, 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]; 
}
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();