[R] How to write a loop in which i has to be in POSIX format?

Hallo, I have a table in which I would like to insert the min and max values of another column (date and time in as.POSIXct Format). This is my row table, where "su" and "sa" are still the same as "Vollzeit": head(treat) Vollzeit Datum Zugnacht su

[R] how di I write a for loop in which i is in POSIX?

Hallo, I have a table in which I would like to insert the min and max values of another colum (date and time in as.POSIXct Format). This is my row table, where "su" and "sa" are still the same as "Vollzeit": head(treat) Vollzeit Datum Zugnacht su