使用 R 复制文件 [英] using R to copy files
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问题描述
As part of a larger task performed in R run under windows, I would like to copy selected files between directories. Is it possible to give within R a command like cp patha/filea*.csv pathb
(notice the wildcard, for extra spice)?
解决方案
I don't think there is a direct way (shy of shelling-out), but something like the following usually works for me.
flist <- list.files("patha", "^filea.+[.]csv$", full.names = TRUE)
file.copy(flist, "pathb")
Notes:
- I purposely decomposed in two steps, they can be combined.
- See the regular expression: R uses true regex, and also separates the file pattern from the path, in two separate arguments.
- note the
^
and$
(beg/end of string) in the regex -- this is a common gotcha, as these are implicit to wildcard-type patterns, but required with regexes (lest some file names which match the wildcard pattern but also start and/or end with additional text be selected as well). - In the Windows world, people will typically add the
ignore.case = TRUE
argument tolist.files
, in order to emulate the fact that directory searches are case insensitive with this OS. - R's
glob2rx()
function provides a convenient way to convert wildcard patterns to regular expressions. For examplefpattern = glob2rx('filea*.csv')
returns a different but equivalent regex.
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