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------------------------------------------------------------
revno: 5958
committer: Lars Helge Overland <larshelge@xxxxxxxxx>
branch nick: dhis2
timestamp: Tue 2012-02-14 19:00:17 +0100
message:
  Impl a partial js port of commons math SimpleRegression class.
added:
  dhis-2/dhis-web/dhis-web-commons-resources/src/main/webapp/dhis-web-commons/javascripts/simpleRegression.js


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=== added file 'dhis-2/dhis-web/dhis-web-commons-resources/src/main/webapp/dhis-web-commons/javascripts/simpleRegression.js'
--- dhis-2/dhis-web/dhis-web-commons-resources/src/main/webapp/dhis-web-commons/javascripts/simpleRegression.js	1970-01-01 00:00:00 +0000
+++ dhis-2/dhis-web/dhis-web-commons-resources/src/main/webapp/dhis-web-commons/javascripts/simpleRegression.js	2012-02-14 18:00:17 +0000
@@ -0,0 +1,61 @@
+
+/**
+ * Partial js port of commons math SimpleRegression class.
+ */
+
+var simpleRegression = new SimpleRegression();
+
+function SimpleRegression()
+{
+	var sumX = 0; // Sum of x values
+	var sumY = 0; // Sum of y values
+	var sumXX = 0; // Total variation in x
+	var sumXY = 0; // Sum of products
+	var n = 0; // Number of observations
+	var xbar = 0; // Mean of accumulated x values, used in updating formulas
+	var ybar = 0; // Mean of accumulated y values, used in updating formulas
+	
+	this.addData = function( x, y )
+	{
+		if ( n == 0 )
+		{
+			xbar = x;
+			ybar = y;
+		}
+		else
+		{
+			var dx = x - xbar;
+			var dy = y - ybar;
+			sumXX += dx * dx * n / ( n + 1 );
+			sumXY += dx * dy * n / ( n + 1 );
+			xbar += dx / ( n + 1 );
+			ybar += dy / ( n + 1 );
+		}
+		
+		sumX += x;
+		sumY += y;
+		n++;
+	};
+	
+	this.predict = function( x )
+	{
+		var b1 = simpleRegression.getSlope();
+		
+		return simpleRegression.getIntercept( b1 ) + b1  * x;
+	};
+	
+	this.getSlope = function()
+	{
+		if ( n < 2 )
+		{
+			return Number.NaN;
+		}
+		
+		return sumXY / sumXX;
+	};
+	
+	this.getIntercept = function( slope )
+	{
+		return ( sumY - slope * sumX ) / n;
+	};
+}