Index: frontends/php/include/classes/validators/CFunctionValidator.php
===================================================================
--- frontends/php/include/classes/validators/CFunctionValidator.php	(revision 53760)
+++ frontends/php/include/classes/validators/CFunctionValidator.php	(working copy)
@@ -189,6 +189,13 @@
 				'args' => $argsIgnored,
 				'value_types' => $valueTypesAll
 			),
+			'rate' => array(
+				'args' => array(
+					array('type' => 'sec_num', 'mandat' => true),
+					array('type' => 'sec_zero', 'can_be_empty' => true)
+				),
+				'value_types' => $valueTypesNum
+			),
 			'regexp' => array(
 				'args' => array(
 					array('type' => 'str', 'mandat' => true),
Index: frontends/php/include/triggers.inc.php
===================================================================
--- frontends/php/include/triggers.inc.php	(revision 53760)
+++ frontends/php/include/triggers.inc.php	(working copy)
@@ -2098,6 +2098,7 @@
 		'nodata' =>		array('value_type' => _('0 or 1'),	'type' => T_ZBX_INT,			'validation' => IN('0,1')),
 		'now' =>		array('value_type' => _('Numeric (integer 64bit)'), 'type' => T_ZBX_INT, 'validation' => NOT_EMPTY),
 		'prev' =>		array('value_type' => $value_type,	'type' => $type_of_value_type,	'validation' => NOT_EMPTY),
+		'rate' =>		array('value_type' => $value_type,	'type' => $type_of_value_type,	'validation' => NOT_EMPTY),
 		'regexp' =>		array('value_type' => _('0 or 1'),	'type' => T_ZBX_INT,			'validation' => IN('0,1')),
 		'str' =>		array('value_type' => _('0 or 1'),	'type' => T_ZBX_INT,			'validation' => IN('0,1')),
 		'strlen' =>		array('value_type' => _('Numeric (integer 64bit)'), 'type' => T_ZBX_INT, 'validation' => NOT_EMPTY),
Index: frontends/php/popup_trexpr.php
===================================================================
--- frontends/php/popup_trexpr.php	(revision 53760)
+++ frontends/php/popup_trexpr.php	(working copy)
@@ -301,6 +301,26 @@
 		'description' =>  _('Previous value is NOT N'),
 		'allowed_types' => $allowedTypesAny
 	),
+	'rate[<]' => array(
+		'description' =>  _('Rate for value over period T is < N'),
+		'params' => $param1SecCount,
+		'allowed_types' => $allowedTypesNumeric
+	),
+	'rate[>]' => array(
+		'description' =>  _('Rate for value over period T is > N'),
+		'params' => $param1SecCount,
+		'allowed_types' => $allowedTypesNumeric
+	),
+	'rate[=]' => array(
+		'description' =>  _('Rate for value over period T is = N'),
+		'params' => $param1SecCount,
+		'allowed_types' => $allowedTypesNumeric
+	),
+	'rate[<>]' => array(
+		'description' =>  _('Rate for value over period T is NOT N'),
+		'params' => $param1SecCount,
+		'allowed_types' => $allowedTypesNumeric
+	),
 	'str[=]' => array(
 		'description' =>  _('Find string V in last (most recent) value. N = 1 - if found, 0 - otherwise'),
 		'params' => $param2SecCount,
Index: src/libs/zbxserver/evalfunc.c
===================================================================
--- src/libs/zbxserver/evalfunc.c	(revision 53760)
+++ src/libs/zbxserver/evalfunc.c	(working copy)
@@ -757,6 +757,118 @@
 
 /******************************************************************************
  *                                                                            *
+ * Function: evaluate_RATE                                                    *
+ *                                                                            *
+ * Purpose: evaluate function 'rate' for the item                             *
+ *                                                                            *
+ * Parameters: item - item (performance metric)                               *
+ *             parameters - number of seconds/values and time shift (optional)*
+ *                                                                            *
+ * Return value: SUCCEED - evaluated successfully, result is stored in 'value'*
+ *               FAIL - failed to evaluate function                           *
+ *                                                                            *
+ * Author: James Burns                                                        *
+ *                                                                            *
+ ******************************************************************************/
+static int	evaluate_RATE(char *value, DC_ITEM *item, const char *function, const char *parameters, time_t now)
+{
+	const char			*__function_name = "evaluate_RATE";
+	int				nparams, arg1, flag, ret = FAIL, i, seconds = 0, nvalues = 0;
+	double meanx=0.0, meany=0.0;
+	double dx=0.0, dy=0.0;
+	double sumdydx=0.0, sumdxdx=0.0;
+	zbx_vector_history_record_t	values;
+
+	zabbix_log(LOG_LEVEL_DEBUG, "In %s()", __function_name);
+
+	zbx_history_record_vector_create(&values);
+
+	if (ITEM_VALUE_TYPE_FLOAT != item->value_type && ITEM_VALUE_TYPE_UINT64 != item->value_type)
+		goto out;
+
+	if (2 < (nparams = num_param(parameters)))
+		goto out;
+
+	if (SUCCEED != get_function_parameter_uint31(item->host.hostid, parameters, 1, &arg1, &flag) || 0 == arg1)
+		goto out;
+
+	if (2 == nparams)
+	{
+		int	time_shift, time_shift_flag;
+
+		if (SUCCEED != get_function_parameter_uint31_default(item->host.hostid, parameters, 2, &time_shift,
+				&time_shift_flag, 0, ZBX_FLAG_SEC) || ZBX_FLAG_SEC != time_shift_flag)
+		{
+			goto out;
+		}
+
+		now -= time_shift;
+	}
+
+	if (ZBX_FLAG_SEC == flag)
+		seconds = arg1;
+	else
+		nvalues = arg1;
+
+	if (FAIL == zbx_vc_get_value_range(item->itemid, item->value_type, &values, seconds, nvalues, now))
+		goto out;
+
+	if (1 < values.values_num)
+	{
+		double	sum = 0;
+
+		if (ITEM_VALUE_TYPE_FLOAT == item->value_type)
+		{
+			for (i = 0; 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
+			
+		}
+		else
+		{
+			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
+			
+		}
+		zbx_snprintf(value, MAX_BUFFER_LEN, ZBX_FS_DBL, sumdydx);
+
+		ret = SUCCEED;
+	}
+	else
+		zabbix_log(LOG_LEVEL_DEBUG, "result for RATE is empty");
+out:
+	zbx_history_record_vector_destroy(&values, item->value_type);
+
+	zabbix_log(LOG_LEVEL_DEBUG, "End of %s():%s", __function_name, zbx_result_string(ret));
+
+	return ret;
+}
+
+/******************************************************************************
+ *                                                                            *
  * Function: evaluate_LAST                                                    *
  *                                                                            *
  * Purpose: evaluate functions 'last' and 'prev' for the item                 *
@@ -1737,6 +1849,10 @@
 	{
 		ret = evaluate_AVG(value, item, function, parameter, now);
 	}
+	else if (0 == strcmp(function, "rate"))
+	{
+		ret = evaluate_RATE(value, item, function, parameter, now);
+	}
 	else if (0 == strcmp(function, "sum"))
 	{
 		ret = evaluate_SUM(value, item, function, parameter, now);
@@ -2224,7 +2340,7 @@
 		{
 			zbx_format_value(value, MAX_BUFFER_LEN, item.valuemapid, item.units, item.value_type);
 		}
-		else if (SUCCEED == str_in_list("abschange,avg,change,delta,max,min,sum", function, ','))
+		else if (SUCCEED == str_in_list("abschange,avg,change,delta,max,min,rate,sum", function, ','))
 		{
 			switch (item.value_type)
 			{
Index: src/zabbix_server/poller/checks_aggregate.c
===================================================================
--- src/zabbix_server/poller/checks_aggregate.c	(revision 53760)
+++ src/zabbix_server/poller/checks_aggregate.c	(working copy)
@@ -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 @@
 {
 	*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 @@
 		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 @@
 		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."));