Polynomial regression I: Difference between revisions

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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',dash:2});
/* 
curve.updateDataArray = function() {
curve.updateDataArray = function() {
     var i, len = data.length;
     var i, len = data.length;
Line 26: Line 27:
     }
     }
}
}
*/
curve.dataX = [1, 100];
curve.dataY = [3, 4];
//curve.update(); // Needed for correct glider position
//curve.update(); // Needed for correct glider position


Line 38: Line 43:


brd.unsuspendUpdate();
brd.unsuspendUpdate();
/*
curve.updateDataArray = function() {
    this.dataX = [];
    this.dataY = [];
}
*/
curve.dataX.length = 0;
curve.dataX.length = 0;
curve.dataY.length = 0;
curve.dataY.length = 0;
curve.update().updateRenderer();
brd.update();


</jsxgraph>
</jsxgraph>

Revision as of 12:36, 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();