Aggregation of object properties

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Detailed Description

Aggregation functions support calculations over properties of multiple objects.

This is used primarily by the collector object in the tape module to define groups (see the group property in aggregate_mkgroupthe collector object). The group can be defined by specifying a boolean series are relationship of object properties, e.g.,

class=node and parent=root 

.

Aggregations also must specify the property that is to be aggregated. Most common aggregations and some uncommon ones are supported. In addition, if the aggregation is over a complex quantity, the aggregation must specific how a double is to be obtained from it, e.g., magnitude, angle, real, imaginary. Some examples aggregate property definitions are

	sum(cost)
	max(power.angle)
	mean(energy.mag)
	std(price)
	

Bug:

Right now, not all allowed aggregations are invariant (meaning that the members of the group do not change over time). However, the collector object requires invariant aggregations. Using an aggregation that isn't invariant will cause the simulation to fail. (ticket #112)

Defines
#define	AF_ABS   0x01
	absolute value aggregation flag
Typedefs
typedef struct s_aggregate	AGGREGATION
	the aggregation type
Functions
AGGREGATION *	aggregate_mkgroup (char *aggregator, char *group_expression)
	This function builds an collection of objects into an aggregation.
double	aggregate_value (AGGREGATION *aggr)
	This function performs an aggregate calculation given by the aggregation.

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Function Documentation

AGGREGATION * aggregate_mkgroup	(	char *	aggregator,
		char *	group_expression
	)

This function builds an collection of objects into an aggregation.

The aggregation can be run using aggregate_value(AGGREGATION*)

Parameters:

aggregator	aggregator (min,max,avg,std,sum,prod,mbe,mean,var,skew,kur,count,gamma)
group_expression	grouping rule; see find_mkpgm(char *)

Definition at line 41 of file aggregate.c.

References AF_ABS, CF_CLASS, class_find_property(), find_first(), output_error(), PT_complex, PT_double, stricmp, unit_convert_ex(), and unit_find().

double aggregate_value

(

AGGREGATION *

aggr

)

This function performs an aggregate calculation given by the aggregation.

Parameters:

aggr	the aggregation to perform

Definition at line 325 of file aggregate.c.

References AF_ABS, CF_CONSTANT, find_first(), find_next(), PT_complex, PT_double, and throw_exception().