From 3116a6d8dbf22c7e4c730db08f9bcaa36cf9d239 Mon Sep 17 00:00:00 2001
From: Daniel Molina <dmolina@opennebula.org>
Date: Tue, 9 Jun 2015 12:58:09 +0200
Subject: [PATCH] feature #3748: Add derivative for graphs

---
 src/sunstone/public/app/utils/graphs.js | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/sunstone/public/app/utils/graphs.js b/src/sunstone/public/app/utils/graphs.js
index 024b7edf69..a9eb8f3df8 100644
--- a/src/sunstone/public/app/utils/graphs.js
+++ b/src/sunstone/public/app/utils/graphs.js
@@ -14,9 +14,9 @@ define(function(require) {
     CONSTRUCTOR
    */
 
-   return {
+  return {
     'plot': _plotGraph
-   }
+  }
 
   /*
     FUNCTION DEFINITIONS
@@ -91,4 +91,21 @@ define(function(require) {
       $.plot(info.div_graph, series, options);
     };
   }
+
+  function derivative(data) {
+    for (var i = 0; i < data.length - 1; i++) {
+      // Each elem is [timestamp, cumulative value]
+      var first = data[i];
+      var second = data[i + 1];
+
+      // value now - value before / seconds
+      var speed = (second[1] - first[1]) / (second[0] - first[0]);
+
+      // The first element is replaced with the second one
+      data[i] = [first[0], speed];
+    }
+
+    // The last elem must be removed
+    data.pop();
+  }
 });