Sample One row within a group

Hi Experts,
I have a table with PatientID, the day of their stay and max vital signs for the day.
I want to create a process that randomly samples one day for each patient.
Table Structure :
PatientID    Day Number    Max_Temp   Max_Resp  Max_SBP    Max_HR
ABC                 1                    98.7            32               90                 72
ABC                 2                    98.8            33               95                 75
ABC                 3                    95              35               90                 78
DEF                 1                    98.7            32               90                 72
DEF                  2                   95              35               90                 78
the output of my process should have one day for each patient picked randomly and should look like as below :

PatientID    Day Number    Max_Temp   Max_Resp  Max_SBP    Max_HR
ABC                 2                    98.8            33               95                 75
DEF                 1                    98.7            32               90                 72

Methods I have tried :

1. I have tried to use sample operator and use balance data option but it requires me to mention each PatientID in
   the parameter list (sample size per class).This is impossible because there are more than 50000 patientID
2. Using R-code(Execute R)  will solve this, but trying to find if there is a way in Rapidminer to solve it.
   
   I am looking for a more automated method to achieve it in Rapidminer 
   
   Please let me know if you need more info.
   Thanks in advance