Controling the x or y limit

Hello - R-experts,

This may sound simple to many --- 
We can specify the x limit by saying xlim = c(0, 20) for example.
 Then the graph will show the range of x -axis between 0 - 20.
 But the coordinate gap will be automatic like 0 then 5 then 15 and 20. 
 Is there any way by which we can set it in a gap of 2 or any number.

 Thank you for any help.
 
 With Regards

 Subhabrata