I need to read two different random lines at a time from a large
ASCII file (120 x 296976) containing space delimited 0-1 entries.
The following code does the job and it's reasonable fast for my needs:
lineNumber = sample(120, 2)
line1 = scan(filename, what = "integer", skip=lineNumber[1]-1, nlines=1)
line2 = scan(filename, what = "integer", skip=lineNumber[2]-1, nlines=1)
> system.time(for (i in 50){
+ lineNumber = sample(120, 2)
+ line1 = scan(filename, what = "integer", skip=lineNumber[1]-1, nlines=1)
+ line2 = scan(filename, what = "integer", skip=lineNumber[2]-1, nlines=1)
+ })
Read 296976 items
Read 296976 items
[1] 14.24 0.12 14.51 NA NA
However, I'm wondering if there's an even faster way to do this. Is there?
> sessionInfo()
R version 2.4.1 (2006-12-18)
i386-pc-mingw32
Juan Pablo Lewinger
Department of Preventive Medicine
Keck School of Medicine
University of Southern California
1540 Alcazar Street, CHP-220
Los Angeles, CA 90089-9011, USA
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