You need to change the appropriate lines to the following (at least):
con <- file("c:/data/perry/data.csv",open="r")
cline <- readLines(con,n=1)
close(con)
(I don't know if more changes are needed to get it working.)
Note that using the connection object in other functions can have side effects on the connection object (which is how a connection "remembers" its point in the file.) (Perhaps more accurately, the side effect is on the internal system data referred to by the R connection object.)
> con <- textConnection(letters)
> con
description class mode text
"letters" "textConnection" "r" "text"
opened can read can write
"opened" "yes" "no"
> readLines(con, 1)
[1] "a"
> readLines(con, 1)
[1] "b"
> con.saved <- con
> readLines(con, 1)
[1] "c"
> readLines(con.saved, 1)
[1] "d"
> readLines(con, 1)
[1] "e"
> identical(con, con.saved)
[1] TRUE
> showConnections()
description class mode text isopen can read can write
3 "letters" "textConnection" "r" "text" "opened" "yes" "no"
>
>hope this helps,
Tony Plate
At Thursday 11:19 AM 8/28/2003 +1200, you wrote:
I have been trying to read a random sample of lines from a file into a data frame using readLines(). The help indicates that readLines() will start from the current line if the connection is open, but presented with a closed connection it will open it, start from the beginning, and close it when finished.
In the code that follows I tried to open the file before reading but apparently without success, because the result was repeated copies of the first line:
flines <- 107165 slines <- 100 selected <- sort(sample(flines,slines)) strvec <- rep("",slines) file("c:/data/perry/data.csv",open="r") isel <- 0 for (iline in 1:slines) { isel <- isel + 1 cline <- readLines("c:/data/perry/data.csv",n=1) if (iline == selected[isel]) strvec[isel] <- cline else isel <- isel - 1 } close("c:/data/perry/data.csv") sel.flows <- read.table(textConnection(strvec), header=FALSE, sep=",")
There was also an error "no applicable method" for close.
Comments gratefully received.
Murray Jorgensen
______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
