R help - Mar 2005 - Dropping coloumns while redaing dtaa from text file.

Hi

I have a huge text file and .dat file from which I want to read data. I do
not need all the columns in the files. I want to extract only some columns
from the .txt file or the .dat file, because reading the entire file is
becoming very difficult due to memory issues. Is it possible to extract a
few columns from .txt or .dat file while reading the data in R?

Thanks
Upasna


-- 
"The past is a history, the future is a mystery, and this moment is a
gift. That is why this moment is called 'the present'." Anonymous

"Upasna Sharma" <upasna at iitb.ac.in> writes:
> Hi
> 
> I have a huge text file and .dat file from which I want to read data. I do
> not need all the columns in the files. I want to extract only some columns
> from the .txt file or the .dat file, because reading the entire file is
> becoming very difficult due to memory issues. Is it possible to extract a
> few columns from .txt or .dat file while reading the data in R?
You're not sayin what tools you are using to read in the first place,
but notice that the colClasses argument to read.table can have NULL
elements. 


-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

On Thu, 10 Mar 2005, Upasna Sharma wrote:
> Hi
>
> I have a huge text file and .dat file from which I want to read data. I do
> not need all the columns in the files. I want to extract only some columns
> from the .txt file or the .dat file, because reading the entire file is
> becoming very difficult due to memory issues. Is it possible to extract a
> few columns from .txt or .dat file while reading the data in R?
Yes.

Look at the use of NULL for 'colClasses' (read.table) or 'what'
(scan),
and also 'flush'.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
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