How to split a dataframe into smaller constituent dataframes

I have read a large dataset into a dataframe using RODBC, the rows of data 
in the dataframe are (integer) timestamped and I would like to divide the 
original dataframe into n smaller dataframes where dataframe 1 contains all 
rows that had timestamps falling in the period 0-x1 minutes, dataframe 2 
contains all rows that had timestamps falling between x1+1 and x2, etc.. 
Does anyone know how to do this?

I would convert all your dates to DateTimeClass (i.e. POSIXct or POSIXlt),
e.g. using strptime, and then loop over them doing your subsetting at each
grid step you specify.  R really has excellent facilities to compute on, or
compare, dates up to Unix timestamp precision.

Alternatively, if the data lives in a DBMS you could simply tailor your
queries to the desired grid sizes and retrieve individual chunks and store
those.

Hth, Dirk

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