?seek -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare [EMAIL PROTECTED] (801) 408-8111
> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Yuchen Luo > Sent: Thursday, April 12, 2007 9:33 AM > To: [EMAIL PROTECTED] > Subject: [R] How to manipulate the pointer of a file? > > Dear friends. > > With file( ) to obtain a pointer of a file, every time we > use scan ( ) to read one row of it, the pointer will point to > the next row of the file. In the following example, d1 and d2 > are obtained the same way but they correspond to different > rows of the same file because the pointer of the file moves > down a row when a row of the file is read. > > The following is an example: > > a1 <- list(name="Fred", wife="Mary", no.children=3) > > a2 <- list(name="Tom", wife="Joy", no.children=9) > > a3 <- list(name="Paul", wife="Alic", no.children=5) > > > write.table(a1, file = "tt.csv", > sep=',',row.names=FALSE,col.name=TRUE) > > write.table(a2, file="tt.csv", sep=',', append=TRUE, row.names=FALSE, > col.names=FALSE) > > write.table(a3, file="tt.csv", sep=',', append=TRUE, row.names=FALSE, > col.names=FALSE) > > > fp=file("tt.csv","r") > > c=scan(file=fp, sep=',', what=list(c1="", c2="", c3=""), flush=TRUE, > nlines=1) > > d1=scan(file=fp, sep=',', what=list(name="", wife="", > no.kids=0), flush=TRUE, nlines=1) > > d1 > > > R output: > > ----------------------- > > $name > > [1] "Fred" > > > > $wife > > [1] "Mary" > > > > $no.kids > > [1] 3 > > ------------------------- > > d2=scan(file=fp, sep=',', what=list(name="", wife="", > no.kids=0), flush=TRUE, nlines=1) > d2 > > > > R Output: > > ------------ > > $name > > [1] "Tom" > > > > $wife > > [1] "Joy" > > > > $no.kids > > [1] 9 > > ---------------------- > > My question is, how to manipulate the pointer of the file > further? For example, what if I need the pointer to go back > to the previous row? > > > Best Wishes > > Yuchen Luo > > [[alternative HTML version deleted]] > > ______________________________________________ > [EMAIL PROTECTED] 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. > ______________________________________________ [EMAIL PROTECTED] 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.