[R] how to judge a virable is a integer?

[PO SU]

Dear usRers,
   I want to judge virable is or not a integer?
  e.g.  is.integer(1)  FALSE   because it is a numeric, but i want it's true.
as.integer may not be used. because i don't know a is 1 or 1.1.





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PO SU
mail: desolator88 at 163.com 
Majored in Statistics from SJTU