[R] Can I improve the efficiency of my scan() command?

[Prof Brian Ripley]

On Sat, 12 Apr 2003, Ko-Kang Kevin Wang wrote:

[...]

> For example, the CSV file has 25 columns but I don't need 3 of them (6, 7, 
> and 22).  What I have done is to scan them in anyway, convert the list 
> into a data frame then remove the 3 columns.  Just wonder if it is 
> possible to simply ignore them in scan() to make the process faster?

Yes: see the help page

      If any of the types is `NULL', the corresponding field is skipped
     (but a `NULL' component appears in the result).

If you don't need a data frame, don't do the conversion.  You might
well find read.table setting colClasses is faster than converting by 
as.data.frame.

-- 
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)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595