Hi every one I wanted to know how do i find the new data entry of the week ?    For Example My data looks like this  Input :  Week   Patient  W1          P1 W1          P2 W1          P3  W2          P1    W2          P2  W2          P4 W3          P3 W3          P4 W3          P5   Desired output    Week  Patient   Flag  W1          P1 W1          P2 W1          P3  W2          P1    W2          P2  W2          P4       New  W3          P3 W3          P4 W3          P5       New   Basically if i am finding the new patient in w6 then I have to look back all possible week and compare how many of these patients have visited me before W6 and if there a new which was not there till w6 then I have to mark that one as a new patient   The weekly data set I have is huge I there is no way i can write individual subset code for everyone  any help will be much appreciated  Thanks in advance  ... View more