added method to prtDataSetClass.m
added method to prtDataSetClass.m

covartech/PRT,jpalves/PRT,covartech/PRT,jpalves/PRT,jpalves/PRT,jpalves/PRT,covartech/PRT,covartech/PRT,jpalves/PRT,jpalves/PRT,covartech/PRT,covartech/PRT