Hi everyone, this is a homework question I have been working on that I just can't get. We just went over working with duplicates and first. last., etc, so I'm thinking the solution would be found using this material. Here is the question (I wrote the data in using datalines):   Given a dataset containing patient id and visit date, write the program to select the earliest 50% of each patient’s records.  For example, if a patient has 4 records, two in 2005 and two in 2006, then the two in 2005 should be selected and output to the new dataset. A partial list of records in the dataset is given below: PTID          VisDate                                                          1                11/05/2005               1                11/05/2005               1                02/15/2005               1                01/14/2004                                                   5                05/05/2005                                                                     5                08/15/2007               2                05/15/2006               2                07/14/2006               2                01/05/2007               2                02/25/2007               3                05/05/2006 ... View more