title: Selecting a range of rows from R data frame
body: <p>I have a data  frame with 1000 rows and I want to perform some operation on it with 100 rows at a time.
  So, I am trying to find out how would I use a counter increment on the number of rows and select 100 rows at a time like 1 to 100, then 101 to 200... uptil 1000 and perform operation on each subset using a for loop. Can anyone please suggest what how can this be done as I could not find out a good method.</p>