[R] count how many row i have in a txt file in a directory

[jim holtman]

Did anyone ever mention the 'countLines' function in R.utils.

On Sun, Feb 26, 2012 at 5:55 PM, Hans Ekbrand <hans at sociologi.cjb.net> wrote:
>
> On Sun, Feb 26, 2012 at 09:39:46AM -0800, Rui Barradas wrote:
> > Hello,
> >
> > > The first step before to create a loop row-by-row is to know
> > > how many rows there are in the txt file without load in R to save
> > > memory
> > > problem.
> > >
> > > some people know the specific function?
> > >
> >
> > I don't believe there's a specific function.
>
> As stated, OP does not need to know the number of lines in the file to
> solve the problem. However, if you want to know that, I'd suggest the
> command wc rather than writing a function in R to accomplish this.
>
> wc is also part of GNU coreutils
>
> $ wc -l foo.csv
> 1138200 foo.csv
>
> > If you want to know how many rows are there in a txt file, try this
> > function.
> >
> > numTextFileLines <- function(filename, header=FALSE, sep=",",
> > nrows=5000){
> >       tc <- file(filename, open="rt")
> >       on.exit(close(tc))
> >       if(header){
> >               # cnames: column names (not used)
> >               cnames <- read.table(file=tc, sep=sep, nrows=1,
> > stringsAsFactors=FALSE)
> >               # cnames <- as.character(cnames)
> >       }
> >       n <- 0
> >       while(TRUE){
> >               x <- tryCatch(read.table(file=tc, sep=sep, nrows=nrows),
> > error=function(e)
> > e)
> >               if (any(grepl("no lines available", unclass(x))))
> >                       break
> >               if(nrow(x) < nrows){
> >                       n <- n + nrow(x)
> >                       break
> >               }
> >               n <- n + nrows
> >       }
> >       n
> > }
>
> But hey, programming R is fun, so why not?
>
> --
> Hans Ekbrand
>
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--
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.