[R] Value Lookup from File without Slurping

[Carlos J. Gil Bellosta]

On Fri, 2009-01-16 at 18:02 +0900, Gundala Viswanath wrote:
> Dear all,
> 
> I have a repository file (let's call it repo.txt)
>  that contain two columns like this:
> 
> # tag  value
> AAA    0.2
> AAT    0.3
> AAC   0.02
> AAG   0.02
> ATA    0.3
> ATT   0.7
> 
> Given another query vector
> 
> > qr <- c("AAC", "ATT")
> 
> I would like to find the corresponding value for each query above,
> yielding:
> 
> 0.02
> 0.7
> 
> However, I want to avoid slurping whole repo.txt into an object (e.g. hash).
> Is there any ways to do that?
> 
> The reason I want to do that because repo.txt is very2 large size
> (milions of lines,
> with tag length > 30 bp),  and my PC memory is too small to keep it.
> 
> - Gundala Viswanath
> Jakarta - Indonesia

Hello,

You can always store your repo.txt into a database, say, SQLite, and
select only the values you want via an SQL query.

Thus, you will prevent loading the full file into memory.

Best regards,

Carlos J. Gil Bellosta
http://www.datanalytics.com