Using R to download zipped data file, extract, and import data

I used CRAN package "downloader" found at http://cran.r-project.org/web/packages/downloader/index.html . Much easier.

download(url, dest="dataset.zip", mode="wb") 
unzip ("dataset.zip", exdir = "./")

Zip archives are actually more a 'filesystem' with content metadata etc. See help(unzip) for details. So to do what you sketch out above you need to

1. Create a temp. file name (eg tempfile())
2. Use download.file() to fetch the file into the temp. file
3. Use unz() to extract the target file from temp. file
4. Remove the temp file via unlink()

which in code (thanks for basic example, but this is simpler) looks like

temp <- tempfile()
download.file("http://www.newcl.org/data/zipfiles/a1.zip",temp)
data <- read.table(unz(temp, "a1.dat"))
unlink(temp)

Compressed (.z) or gzipped (.gz) or bzip2ed (.bz2) files are just the file and those you can read directly from a connection. So get the data provider to use that instead :)

Just for the record, I tried translating Dirk's answer into code :-P

temp <- tempfile()
download.file("http://www.newcl.org/data/zipfiles/a1.zip",temp)
con <- unz(temp, "a1.dat")
data <- matrix(scan(con),ncol=4,byrow=TRUE)
unlink(temp)

For Mac (and I assume Linux)...

If the zip archive contains a single file, you can use the bash command funzip, in conjuction with fread from the data.table package:

library(data.table)
dt <- fread("curl http://www.newcl.org/data/zipfiles/a1.zip | funzip")

In cases where the archive contains multiple files, you can use tar instead to extract a specific file to stdout:

dt <- fread("curl http://www.newcl.org/data/zipfiles/a1.zip | tar -xf- --to-stdout *a1.dat")