--- C:/Users/JBurns/AppData/Local/Temp/checks_aggregate.c-revBASE.svn000.tmp.c	Tue Sep 23 14:58:53 2014
+++ C:/SVN/ZABBIX/2.4.2/src/zabbix_server/poller/checks_aggregate.c	Sun May 24 23:12:22 2015
@@ -29,6 +29,7 @@
 #define ZBX_VALUE_FUNC_SUM	3
 #define ZBX_VALUE_FUNC_COUNT	4
 #define ZBX_VALUE_FUNC_LAST	5
+#define ZBX_VALUE_FUNC_RATE	6
 
 /******************************************************************************
  *                                                                            *
@@ -184,7 +185,63 @@ static void	evaluate_history_func_last(zbx_vector_
 {
 	*result = values->values[0].value;
 }
+/******************************************************************************
+ *                                                                            *
+ * Function: evaluate_history_func_rate                                       *
+ *                                                                            *
+ * Purpose: calculate the rate of change for the history value ZBXNEXT-2374   *
+ *                                                                            *
+ * Parameters: values     - [IN] a vector containing history values           *
+ *             value_type - [IN] the type of values. Only float/uint64        *
+ *                          values are supported.                             *
+ *             result - [OUT] the result value/second (from timestamp)        *
+ *                                                                            *
+ * Author: James Burns                                                        *
+ *                                                                            *
+ ******************************************************************************/ 
+static void evaluate_history_func_rate(zbx_vector_history_record_t *values, int value_type, history_value_t *result) {
 
+	int	i;
+	double meanx=0.0, meany=0.0;
+	double dx=0.0, dy=0.0;
+	double sumdydx=0.0, sumdxdx=0.0;
+
+	if (ITEM_VALUE_TYPE_UINT64 == value_type)
+	{
+		for (i = 0; i < values->values_num; i++){
+			meanx += values->values[i].timestamp.sec;
+			meany += values->values[i].value.ui64;
+		}
+		meanx /= values->values_num;
+		meany /= values->values_num;	
+
+		for (i = 1; i < values->values_num; i++){
+			dx = (values->values[i].timestamp.sec - meanx);
+			dy = (values->values[i].value.ui64-meany);
+			sumdydx += (dy*dx);
+			sumdxdx += (dx*dx);
+		}
+		sumdydx /= sumdxdx;//produce the gradient and store in sumdydx
+		result->ui64 = sumdydx;
+	}
+	else {
+		for (i = 1; i < values->values_num; i++){
+			meanx += values->values[i].timestamp.sec;
+			meany += values->values[i].value.dbl;
+		}
+		meanx /= values->values_num;
+		meany /= values->values_num;
+		for (i = 1; i < values->values_num; i++){
+			dx = (values->values[i].timestamp.sec - meanx);
+			dy = (values->values[i].value.dbl-meany);
+			sumdydx += (dy*dx);
+			sumdxdx += (dx*dx);
+		}
+		sumdydx /= sumdxdx;//produce the gradient and store in sumdydx
+		result->dbl = sumdydx;
+	}
+}
+
 /******************************************************************************
  *                                                                            *
  * Function: evaluate_history_func                                            *
@@ -225,6 +282,9 @@ static void	evaluate_history_func(zbx_vector_histo
 		case ZBX_VALUE_FUNC_LAST:
 			evaluate_history_func_last(values, value_type, result);
 			break;
+		case ZBX_VALUE_FUNC_RATE:
+			evaluate_history_func_rate(values, value_type, result);
+			break;
 	}
 }
 
@@ -509,6 +569,8 @@ int	get_value_aggregate(DC_ITEM *item, AGENT_RESUL
 		item_func = ZBX_VALUE_FUNC_COUNT;
 	else if (0 == strcmp(tmp, "last"))
 		item_func = ZBX_VALUE_FUNC_LAST;
+	else if (0 == strcmp(tmp, "rate"))
+		item_func = ZBX_VALUE_FUNC_RATE;
 	else
 	{
 		SET_MSG_RESULT(result, zbx_strdup(NULL, "Invalid third parameter."));