[R] Large database help

[Roger D. Peng]

You can read fixed-width-files with read.fwf().  But my rough calculation says 
that your dataset will require 40GB of RAM.  I don't think you'll be able to 
read the entire thing into R.  Maybe look at a subset?

-roger

Rogerio Porto wrote:
> Hello all.
> 
> I have a large .txt file whose variables are fixed-columns, 
> ie, variable V1 goes from columns 1 to 7, V2 from 8 to 23 etc.
> This is a 60GB file with 90 variables and 60 million observations.
> 
> I'm working with a Pentium 4, 1GB RAM, Windows XP Pro.
> I tried the following code just to see if I could work with 2 variables
> but it seems not possible: 
> R : Copyright 2005, The R Foundation for Statistical Computing
> Version 2.2.1  (2005-12-20 r36812)
> ISBN 3-900051-07-0
>> gc()
>          used (Mb) gc trigger (Mb) max used (Mb)
> Ncells 169011  4.6     350000  9.4   350000  9.4
> Vcells  62418  0.5     786432  6.0   289957  2.3
>> memory.limit(size=4090)
> NULL
>> memory.limit()
> [1] 4288675840
>> system.time(a<-matrix(runif(1e6),nrow=1))
> [1] 0.28 0.02 2.42   NA   NA
>> gc()
>           used (Mb) gc trigger (Mb) max used (Mb)
> Ncells  171344  4.6     350000  9.4   350000  9.4
> Vcells 1063212  8.2    3454398 26.4  4063230 31.0
>> rm(a)
>> ls()
> character(0)
>> system.time(a<-matrix(runif(60e6),nrow=1))
> Error: not possible to alocate vector of size 468750 Kb
> Timing stopped at: 7.32 1.95 83.55 NA NA 
>> memory.limit(size=5000)
> Erro em memory.size(size) : .....4GB
> 
> So my questions are:
> 1) (newbie) how can I read fixed-columns text files like this?
> 2) is there a way I can analyze (statistics like correlations, cluster etc)
>     such a large database neither increasing RAM nor changing to 64bit
>     machine but still using R and not using a sample? How? 
> 
> Thanks in advance.
> 
> Rogerio.
> 
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