Hi Jim, I was trying to use your template without success. With the toy data below, could you explain how to use this template to change all "b"s to "z"s -- just as an exercise, reading in 3 lines at a time. I need to use this strategy for a larger problem, but I haven't been able to get the basics working.
Thanks, Juliet myData <- structure(list(V1 = 1:11, V2 = structure(c(2L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 2L, 3L), .Label = c("a", "b", "c"), class = "factor"), V3 = structure(c(2L, 1L, 2L, 1L, 2L, 1L, 1L, 2L, 2L, 2L, 3L), .Label = c("a", "b", "c"), class = "factor"), V4 = structure(c(1L, 1L, 2L, 2L, 1L, 2L, 2L, 1L, 2L, 1L, 2L), .Label = c("a", "b"), class = "factor"), V5 = c(-0.499071939558026, 1.51341011554134, 1.93754671209923, 0.331061227463955, 0.280752001959284, 0.964635079229074, 0.624397908891502, -0.807600774484419, -1.76452730888732, 0.546080229326458, 12.3)), .Names = c("V1", "V2", "V3", "V4", "V5"), class = "data.frame", row.names = c(NA, -11L)) On Sun, Aug 15, 2010 at 1:06 PM, jim holtman <jholt...@gmail.com> wrote: > For efficiency of processing, look at reading in several > hundred/thousand lines at a time. One line read/write will probably > spend most of the time in the system calls to do the I/O and will take > a long time. So do something like this: > > con <- file('yourInputFile', 'r') > outfile <- file('yourOutputFile', 'w') > while (length(input <- readLines(con, n=1000) > 0){ > for (i in 1:length(input)){ > ......your one line at a time processing > } > writeLines(output, con=outfile) > } > > On Sun, Aug 15, 2010 at 7:58 AM, Data Analytics Corp. > <w...@dataanalyticscorp.com> wrote: >> Hi, >> >> I have an upcoming project that will involve a large text file. I want to >> >> 1. read the file into R one line at a time >> 2. do some string manipulations on the line >> 3. write the line to another text file. >> >> I can handle the last two parts. Scan and read.table seem to read the whole >> file in at once. Since this is a very large file (several hundred thousand >> lines), this is not practical. Hence the idea of reading one line at at >> time. The question is, can R read one line at a time? If so, how? Any >> suggestions are appreciated. >> >> Thanks, >> >> Walt >> >> ________________________ >> >> Walter R. Paczkowski, Ph.D. >> Data Analytics Corp. >> 44 Hamilton Lane >> Plainsboro, NJ 08536 >> ________________________ >> (V) 609-936-8999 >> (F) 609-936-3733 >> w...@dataanalyticscorp.com >> www.dataanalyticscorp.com >> >> _____________________________________________________ >> >> >> -- >> ________________________ >> >> Walter R. Paczkowski, Ph.D. >> Data Analytics Corp. >> 44 Hamilton Lane >> Plainsboro, NJ 08536 >> ________________________ >> (V) 609-936-8999 >> (F) 609-936-3733 >> w...@dataanalyticscorp.com >> www.dataanalyticscorp.com >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > > > -- > Jim Holtman > Cincinnati, OH > +1 513 646 9390 > > What is the problem that you are trying to solve? > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.