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I have come across this comand 

unique(StudentGroups[,.(groupID, start, end, student)])

I was wondereing what is the purpose of the . ?

Nneka
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    It is creating a `list`. You can replace with `list(groupID, ..` – akrun Feb 20 '20 at 20:32
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    Is `StudentGroups` a `data.table`? Otherwise I don't know that `.` is defined. Assuming it is (and just adding clarity and definition to @akrun's comment): from `?data.table`: "The expression `.()` is a *shorthand* alias to `list()`; they both mean the same. (An exception is made for the use of `.()` within a call to `bquote`, where `.()` is left unchanged.)" – r2evans Feb 20 '20 at 20:38
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    Some discussion of what the `.` can mean can be found: https://stackoverflow.com/a/27560562/2372064. It entirely depends on the context. – MrFlick Feb 20 '20 at 20:50

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