[R] Matching where the source file has one record/ subject and the to-be-matched file has multiple records/subect

[Sorkin, John]

I am not showing code, because I don't know how to write the code. I know that MatchIt performs propensity score matching, but I don't know how to use the function to perform the match I want to conduct.

I have two files
File 1: a list of n  records, 1 record/subject. Each record has a subject number and a date
File 2: a list of m records m>>n with multiple records/subject but each record has a distinct date. All records for a given subject in file 2 have the same subject number, but each record has a different date.

I want to match each record from file 1 with a single record from file 2 based on date. Once a record from file 2 is matched with a record from file 1, I want to remove all records from file 2 for the subject who was used in the match with the subject from file 1 so that the subject from file 2 will not be used in any future match.


Example
file 1                                          file 2
subject   date                              subject   date
1              01/01/2020                  100   01/01/2020
2              01/01/2021                  100   01/10/2021
3                                                   101  02/01/2021
  
Subject 1 from file 1 is a perfect match for subject 100 from file2. The subjects are matched.
All data from file 2 is removed for subject 100.
Subject 2 from file 1 is then matched with subject 101 from file 2.
If all records from subject 100 had not been removed from file2, subject 2 would have been matched to subject 100 date 01/10/2021. I don't want this to happen. Once subject 100 is used to match subject 1, I don't want any other person from file 1 to be matched with subject 100.

I hope you can help me with this, I suspect, not uncommon matching problem!

Thank you,
John

John David Sorkin M.D., Ph.D.
Professor of Medicine, University of Maryland School of Medicine;
Associate Director for Biostatistics and Informatics, Baltimore VA Medical Center Geriatrics Research, Education, and Clinical Center; 
Former PI Biostatistics and Informatics Core, University of Maryland School of Medicine Claude D. Pepper Older Americans Independence Center;
Senior Statistician University of Maryland Center for Vascular Research;

Division of Gerontology, Geriatrics and Palliative Medicine,
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
Cell phone 443-418-5382