I have a dataset and would like to select only the smallest date between each primary key ( MATRICULA column). Here is the example of my DF:
MATRICULA <- c(1,1,3,3,3,4,5,5,5,5,6)
DATA <- c('15/01/2018', '10/12/2017', '20/11/2017',...
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19.12.2018 / 13:44