[R] Dealing With Extremely Large Files

[jim holtman]

You can always setup a "connection" and then read in the number of
lines you need for the analysis, write out the results and then read
in the next ones.  I have also used 'filehash' to initially read in
portions of a file and then write the objects into the database.
These are quickly retrieved if I want to make subsequent passes
through the data.

A 100,000 rows will also probably tax your machine since if these are
numeric, you will need 800MB to store a since copy of the object and
you will probably need 3-4X that amount (a total of 4GB of physical
memory) if you are doing any processing that might make copies.
Hopefully you are running on a 64-bit system with lots of memory.

On Fri, Sep 26, 2008 at 3:55 PM, zerfetzen <zerfetzen at yahoo.com> wrote:
>
> Hi,
> I'm sure that a large fixed width file, such as 300 million rows and 1,000
> columns, is too large for R to handle on a PC, but are there ways to deal
> with it?
>
> For example, is there a way to combine some sampling method with read.fwf so
> that you can read in a sample of 100,000 records, for example?
>
> Something like this may make analysis possible.
>
> Once analyzed, is there a way to, say, read in only x rows at a time, save
> and score each subset separately, and finally append them back together?
>
> I haven't seen any information on this, if it is possible.  Thank you for
> reading, and sorry if the information was easily available and I simply
> didn't find it.
> --
> View this message in context: http://www.nabble.com/Dealing-With-Extremely-Large-Files-tp19695311p19695311.html
> Sent from the R help mailing list archive at Nabble.com.
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?