[R] How to split a dataframe into smaller constituent dataframes

Dirk Eddelbuettel edd at debian.org
Mon May 19 00:27:41 CEST 2003

On Sun, May 18, 2003 at 10:11:11PM +0000, Neil Osborne wrote:
> 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

Hth, Dirk

Don't drink and derive. Alcohol and analysis don't mix.

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