private boolean evaluatePrintClause(String str) {
		if (str == null)
			return false;
		str = format(str);
		// average over the selected particles
		Matcher matcher = MEAN.matcher(str);
		if (matcher.find()) {
			out(ScriptEvent.SUCCEEDED, str + " = " + getAverage(str.substring(1, str.length() - 1)));
			return true;
		}
		out(ScriptEvent.SUCCEEDED, str);
		return true;
	}