[R] re ading specific columns

David Winsemius dwinsemius at comcast.net
Tue Nov 18 07:55:35 CET 2008

On Nov 18, 2008, at 12:57 AM, kayj wrote:

> I have a huge txt file and I only want to get out of it  column 3  
> and 7.
> I tried to read the whole file and then extract the two columns, but  
> I ran
> into a memory problem  since the file is huge.
> Is it possible just to tell R to read these two columns without  
> reading the
> whole file?

?read.table  # read the documentation for colClasses carefully

something along the lines of:
in.frame <- read.table(file = "c//folder/filename.ext", colClasses =  
c("NULL","NULL","character", "NULL", "NULL","NULL","NULL","character"))

You need to add as many NULLs as there are additional records in the  
longest input line. It may be helpful to first run count.fields(). You  
might get a more specific answer if you defined "huge". You should  
also look at the FAQ regarding memory issues. There are also database  
oriented solutions available.

David Winsemius

> Thanks
> -- 
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