[R] plz help. how to filter/group/sort data on mass data

[bestbird]

 I have know how to sort and filter and group.
can anyone answer my another question?
Is there any function in R like *lead *and *lag * in SQL. They are relative
position function. We can use them to solve problem such as : on
year-on-year basis, link relative ratio

can anyone give a tips?

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