Difference between revisions of "Polynomial regression I"

From JSXGraph Wiki
Jump to navigationJump to search
Line 14: Line 14:
 
var brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-2, 100, data.length+2, -70], grid: false, axis:true});
 
var brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-2, 100, data.length+2, -70], grid: false, axis:true});
  
//brd.suspendUpdate();
+
brd.suspendUpdate();
 
var s = brd.create('slider',[[10,70],[80,70],[0,1,1]],{name:'scale'});     
 
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 deg = brd.create('slider',[[10,90],[80,90],[1,1,10]],{name:'degree',snapWidth:1});     
Line 26: Line 26:
 
     }
 
     }
 
}
 
}
 +
curve.update();
  
 
var regressionPolynomial = JXG.Math.Numerics.regressionPolynomial(deg, datax, curve.dataY);
 
var regressionPolynomial = JXG.Math.Numerics.regressionPolynomial(deg, datax, curve.dataY);
Line 36: Line 37:
 
             {strokeColor:'black',fontSize:18});     
 
             {strokeColor:'black',fontSize:18});     
  
//brd.unsuspendUpdate();
+
brd.unsuspendUpdate();
 
</jsxgraph>
 
</jsxgraph>
  

Revision as of 11:47, 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:18});     
brd.unsuspendUpdate();