[R] Reading data into R

[Rubén Roa-Ureta]

BEP wrote:
> Hello all,
> 
> I am working with a very large data set into R, and I have no interest in
> reviving my SAS skills.  To do this, I will need to drop unwanted variables
> given the size of the data file.  The most common strategy seems to be
> subsetting the data after it is read into R.  Unfortunately, given the size
> of the data set, I can't get the file read and then subsquently do the
> subset procedure.  I would be appreciative of help on the following:
> 
> 1.  What are the possibilities of reading in just a small set of variables
> during the <read.table> statement (or another 'read' statement)?  That is,
> is it possible specify just the variables that I want to keep?
> 
> 2.  Can I randomly select a set of observations during the 'read' statement?
> 
> 
> I have searched various R resources for this information, so if I am simply
> overlooking a key resource on this issue, pointing that out to me would be
> greatly appreciated.
> 
> Thanks in advance.
> 
> Brian

Check this for input of specific columns from a large data matrix:
mysubsetdata<-do.call("cbind",scan(file='location and name of your 
file',what=list(NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,0,NULL,0,NULL,NULL),flush=TRUE))
This will input only columns 10 and 11 into 'mysubsetdata'.
With this method you can work out the way to select random columns.
HTH
Rubén