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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