I have been trying it out. There is some problem in the code that still needs to be figured out.
For the first 9 files, paste("wb-0", i, "vc.dbf", sep="") works fine.
But as you rightly guessed, I have more files.
So when I use paste("wb-", formatC(i, width=2, flag="0"), "vc.dbf", sep=""), dbf.read does not work.
formatC works find if I use it in cat(paste.................). It displays the file names correctly.
But when I use it in dbf.read, it gives the following error.
***********************
res[[i]] <- maptools:::dbf.read(paste("wb-", format(i, width=2,flag=0), "vc.dbf", sep=""))
Error in maptools:::dbf.read(paste("wb-", format(i, width=2,flag=0), "vc.dbf", sep=""))
Error in maptools:::dbf.read(paste("wb-", format(i, width = 2, flag = 0), :
unable to open DBF file
***********************
Of course, the data files are all right. I can read them individually.
What do you think could be the problem?
Vikas
Kevin Bartz wrote:
Roger Bivand wrote:
On Fri, 1 Oct 2004, Vikas Rawal wrote:
I want to read data from a number of files into R.
Reading individual files one by one requires writing enormous amount of code that will look something like the following.
**************** maptools:::dbf.read("wb-01vc.dbf")->dist1 maptools:::dbf.read("wb-02vc.dbf")->dist2 maptools:::dbf.read("wb-03vc.dbf")->dist3 maptools:::dbf.read("wb-04vc.dbf")->dist4 maptools:::dbf.read("wb-05vc.dbf")->dist5 maptools:::dbf.read("wb-06vc.dbf")->dist6 maptools:::dbf.read("wb-07vc.dbf")->dist7 maptools:::dbf.read("wb-08vc.dbf")->dist8 maptools:::dbf.read("wb-09vc.dbf")->dist9 *****************
In this case, you could pre-allocate a list and:
res <- vector(mode="list", length=9)
for (i in 1:length(res)) res[[i]] <- maptools:::dbf.read(paste("wb-0", i, "vc.dbf", sep=""))
res <- vector(mode="list", length=9) for (i in 1:length(res)) cat(paste("wb-0", i, "vc.dbf", sep=""), "\n")
wb-01vc.dbf wb-02vc.dbf wb-03vc.dbf ...
gives a check on what file names are being used.
For 10 to 99 preserving the 01-09, use paste("wb-", formatC(i, width=2, flag="0"), "vc.dbf", sep="").
If the token is a character (string) that varies, you can roll out a character vector of tokens first and step along it.
res <- vector(mode="list", length=length(LETTERS))
for (i in 1:length(res)) cat(paste("wb-", LETTERS[i], "vc.dbf", sep=""),
+ "\n") wb-Avc.dbf wb-Bvc.dbf wb-Cvc.dbf ...
Is there a better way of doing this?
Vikas
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Good call. Here's a somewhat more R-ified version:
res <- lapply(paste("wb-", formatC(1:99, width=2, flag="0"), "vc.dbf", sep=""), maptools:::dbf.read)
Kevin
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