[R] Date and selection

[Chung-hong Chan]

Dear R experts,

Suppose I have a data.frame recording the date and test results of
some subjects like this:

Name Date results
John 01/01/1991 2
John 02/01/1991 3
John 09/0101991 4
Micheal 02/01/1991 4
Micheal 04/01/1991 5
....

How to select the earliest (or latest) test result from all subjects?

Thank you.

Regards,

CH



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