R is nice because it can deal with other less flexible software and many people
must use Excel at their jobs.
You can write a function that detects if your file ends with a newline and use
it
to add a newline exactly when needed. E.g., the following compares the last
few bytes in the file to the newline pattern that you specify and returns TRUE
if
the file ends with a newline. It reads in chunks so it doesn't waste space
with very
large files. In your situation you can do
if (!fileEndsWithNewline(outputFile)) cat("\n", append=TRUE, file=outputFile)
before each call to write.table(append=TRUE).
I suppose the check should be modified to check that the file is not empty, as
you don't
want a newline before any of your data in that case.
fileEndsWithNewline <- function(file, chunksize=4096, newline=if
(.Platform$OS.type=="windows") "\r\n" else "\n")
{
rawNewline <- charToRaw(newline)
stopifnot(chunksize >= length(rawNewline))
conn <- file(file, "rb")
on.exit(close(conn))
prevChunk <- raw()
repeat {
thisChunk <- readBin(conn, what="raw", n=chunksize)
if (length(thisChunk) < chunksize) {
# concatenate in case newline is spread over two chunks
lastChunk <- c(prevChunk, thisChunk)
break
}
prevChunk <- thisChunk
}
length(lastChunk) >= length(rawNewline) && all(rawNewline ==
tail(lastChunk, 2))
}
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf
> Of Jeff Newmiller
> Sent: Saturday, April 20, 2013 8:14 AM
> To: Vinny Moriarty; r-help@r-project.org
> Subject: Re: [R] Editing data sheet issue with write.table append
>
> a) Your terminology "data sheet" is foreign to R (and this mailing list). It
> implies a
> computing model that R does not use.
>
> b) You appear to be complaining about the behavior of software other than R
> on the R-
> help mailing list, which is pointless.
>
> c) I think the chances of adding code to base R to fix the broken behavior of
> another
> software package is highly unlikely, particularly when from your description
> you might or
> might not end up with the missing newline depending on whether you choose to
> modify
> any particular file outside R. Putting in a newline every time would make R
> just as broken
> as Excel.
>
> 4) You can put in newlines before or after your write.table call using the
> ?cat function.
> Read the data input and output manual for details... but beware that
> write.table is a
> high-level function that intentionally tries to generate a coherent
> representation of the
> data table as a single block of text. If you need to tweak within that text
> then you may
> need to make your own special output function.
> ---------------------------------------------------------------------------
> Jeff Newmiller The ..... ..... Go Live...
> DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go...
> Live: OO#.. Dead: OO#.. Playing
> Research Engineer (Solar/Batteries O.O#. #.O#. with
> /Software/Embedded Controllers) .OO#. .OO#. rocks...1k
> ---------------------------------------------------------------------------
> Sent from my phone. Please excuse my brevity.
>
> Vinny Moriarty <vwmoria...@gmail.com> wrote:
>
> >I'm running R 2.15.2 on Max OS X 10.6.8
> >
> >
> >If I write a simple file
> >
> >Data1<-1
> >DF<-data.frame(Data1)
> >colnames(DF)<-"Col1"
> >
> >and write to a csv file
> >
> >write.table(DF,file="Data.csv",sep=",",row.names=FALSE,col.names=TRUE)
> >
> >I can then append to it no problem
> >
> >Data2<-2
> >Data3<-4
> >
> >
> >DF2<-data.frame(Data2)
> >DF3<-data.frame(Data3)
> >
> >write.table(DF2,file="Data.csv",sep=",",row.names=FALSE,col.names=FALSE,append=T
> RUE)
> >write.table(DF3,file="Data.csv",sep=",",row.names=FALSE,col.names=FALSE,append=T
> RUE)
> >
> >
> >All good so far.
> >
> >But the problem arises if I then need to edit the data sheet and
> >continue
> >to append using the above code. If I open up the data sheet in excel
> >and
> >delete a line, the next time I try and append the data as above the
> >first
> >new line of data starts at the end of the last row of data (though all
> >subsequent new lines are appended properly).
> >
> >I'm sure when I manually delete the line in excel I am removing the
> >invisible carriage return character, causing the first line of new data
> >to
> >be added onto where the carriage return used to be.
> >
> >Is there a way to specify in append=TRUE to always start with a new
> >line of
> >data in the spreadsheet? Failing that, is there a work around to avoid
> >this
> >problem?
> >
> > [[alternative HTML version deleted]]
> >
> >______________________________________________
> >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.
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
