public double getAggregate( String dsName, String consolFun ) throws RrdException
	{
		Source src = getSource( dsName );

		if( consolFun.equalsIgnoreCase("MAX") )
			return src.getAggregate( Source.AGG_MAXIMUM );
		else if ( consolFun.equalsIgnoreCase("MIN") )
			return src.getAggregate( Source.AGG_MINIMUM );
		else if ( consolFun.equalsIgnoreCase("LAST") )
			return src.getAggregate( Source.AGG_LAST);
		else if ( consolFun.equalsIgnoreCase("FIRST") )
			return src.getAggregate( Source.AGG_FIRST );
		else if ( consolFun.equalsIgnoreCase("TOTAL") )
			return src.getAggregate( Source.AGG_TOTAL );
		else if ( consolFun.equalsIgnoreCase("AVERAGE") )
			return src.getAggregate( Source.AGG_AVERAGE );
		else
			throw new RrdException("Unsupported consolidation function [" + consolFun + "]");
	}