function winloss() {
		var r = randu();
		if ( r > 0.66 ) {
			return 2;
		}
		if ( r > 0.33 ) {
			return 1;
		}
		if ( r > 0.15 ) {
			return -1;
		}
		return -2;
	}
Returns a win-loss chart datum.

@private
@returns {number} datum