From 14b54aded0196a31d554d44610fe404b4d1a7fbb Mon Sep 17 00:00:00 2001
From: "Steve L. Nyemba" <nyemba@gmail.com>
Date: Mon, 18 May 2015 11:28:16 -0500
Subject: [PATCH] Update on dom.js and math functions

---
 dom.js      |  9 +++++----
 ext/math.js | 33 ++++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/dom.js b/dom.js
index 627bb4c..4c2530d 100644
--- a/dom.js
+++ b/dom.js
@@ -35,12 +35,13 @@ jx.dom.exists = function(id){
  * @returns {undefined}
  */
 jx.dom.remove = function(id){
+    var _item = null;
     if (id.constructor == String){
-            item = jx.dom.get.instance(id)
+            _item = jx.dom.get.instance(id)
     }else{
-            item = id ;
+            _item = id ;
     }
-    item.parentNode.removeChild(item) ;
+    _item.parentNode.removeChild(_item) ;
     
 }
 
@@ -51,7 +52,7 @@ jx.dom.remove = function(id){
  * @param _child    child dom object 
  */
 jx.dom.append = function(id,_child){
-	_parent = jx.dom.get.instance(id) ;
+	var _parent = jx.dom.get.instance(id) ;
 	_parent.appendChild(_child) ;
 }
 
diff --git a/ext/math.js b/ext/math.js
index 6b466db..949c0fb 100644
--- a/ext/math.js
+++ b/ext/math.js
@@ -95,6 +95,17 @@ jx.math.avg = function(lxi,lni){
     }
 };
 
+/**
+* This function will repete a value a given number of times
+* @pre times > 0
+*/
+jx.math.rep = function(value,times){
+	var lvalues = []
+	for(var i=0; i < times; i++){
+		lvalues.push(value) ;
+	}
+	return lvalues;
+}
 jx.math.mean = jx.math.avg ;
 jx.math.pow = Math.pow
 jx.math.sd = function(lxi,lni){
@@ -103,7 +114,6 @@ jx.math.sd = function(lxi,lni){
 
     sqr = [] ;
     for(var i=0; i < lxi.length ;i++){
-		console.log(lxi[i])
        sqr[i] = jx.math.pow((Number(lxi[i])-mean),2 ) ;
     }
 
@@ -111,6 +121,27 @@ jx.math.sd = function(lxi,lni){
 
     return jx.math.sqrt(total/(N-1)) ;
 } ;
+/**
+* This function computes the correlation between two vectors
+* @pre x1.length == x2.length
+*/
+jx.math.cor = function(x1,x2){
+	return jx.math.cov(x1,x2) / (jx.math.sd(x1)*jx.math.sd(x2))
+}
+/**
+* This function will compute the covariance of 2 vectors
+* @pre x1.length == x2.length
+*/
+jx.math.cov = function(x1,x2){
+	var u1 = jx.math.mean(x1) ;
+	var u2 = jx.math.mean(x2) ;
+	var N = x1.length ;
+	var value = 0
+	for(var i in x1){
+		value += (x1[i] - u1) * (x2[i] - u2)
+	}
+	return value / (N - 1)
+}
 
 /**
 * Computes the factorial of a given value