[R] How to import specific column(s) using "read.table"?

[F Duan]

Thanks a lot. 

Your way works perfect. And one more tiny question related to your codes:

My data file has many columns to be omitted (suppose the first 20 ones), but I 
found "scan(myfile, what=list(rep(NULL, 20), rep(0, 5))" doesn't work. I had to 
to type "NULL" 20 times and "0" five times in the "list(...)". 

But anyway, it works and saves a lot of memory for me. Thank you again.

Frank 


Quoting Gabor Grothendieck <ggrothendieck at myway.com>:

> Gabor Grothendieck <ggrothendieck <at> myway.com> writes:
> 
> : 
> : F Duan <f.duan <at> yale.edu> writes:
> : 
> : > I have a very big tab-delim txt file with header and I only want to
> import 
> : > several columns into R. I checked the options for Â"read.tableÂ" and only
> 
> : 
> : Try using scan with the what=list(...) and flush=TRUE arguments.  
> : For example, if your data looks like this:
> : 
> : 1 2 3 4 
> : 5 6 7 8 
> : 9 10 11 12
> : 13 14 15 16
> : 
> : then you could read columns 2 and 4 into a list with:
> : 
> 
> oops. That should be 1 and 3.
> 
> :    scan(myfile, what = list(0, NULL, 0), flush = TRUE)
> : 
> : or read in and convert to a data frame via:
> : 
> :    do.call("cbind", scan(myfile, what = list(0, NULL, 0), flush = TRUE))
> 
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