26 messages · Gundala Viswanath, jim holtman, Henrique Dallazuanna +8 more
Messages 1–25 of 26
Dear all, The basename() function returns the extension also:
myfile <- "path1/path2/myoutput.txt" basename(myfile)
[1] "myoutput.txt" Is there any other function where it just returns plain base: "myoutput" i.e. without 'txt' - Gundala Viswanath Jakarta - Indonesia
You can use 'sub' to get rid of the extensions:
sub("^([^.]*).*", "\\1", 'filename.extension')
[1] "filename"
sub("^([^.]*).*", "\\1", 'filename.extension.and.more')
[1] "filename"
sub("^([^.]*).*", "\\1", 'filename without extension')
[1] "filename without extension"
Dear all, The basename() function returns the extension also:
myfile <- "path1/path2/myoutput.txt" basename(myfile)
[1] "myoutput.txt" Is there any other function where it just returns plain base: "myoutput" i.e. without 'txt' - Gundala Viswanath Jakarta - Indonesia
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve?
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G'day all, On Fri, 9 Jan 2009 08:12:18 -0200
Try this also: substr(basename(myfile), 1, nchar(basename(myfile)) - 4)
Or, in case that the extension has more than three letters or "myfile" is a vector of names: R> myfile <- "path1/path2/myoutput.txt" R> sapply(strsplit(basename(myfile),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" R> myfile2 <- c(myfile, "path2/path3/myoutput.temp") R> sapply(strsplit(basename(myfile2),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" R> myfile3 <- c(myfile2, "path4/path5/my.out.put.xls") R> sapply(strsplit(basename(myfile3),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" "my.out.put" HTH. Cheers, Berwin
On Fri, Jan 9, 2009 at 12:10 AM, Gundala Viswanath <gundalav at gmail.com>wrote:
Dear all, The basename() function returns the extension also:
myfile <- "path1/path2/myoutput.txt" basename(myfile)
[1] "myoutput.txt" Is there any other function where it just returns plain base: "myoutput" i.e. without 'txt' - Gundala Viswanath Jakarta - Indonesia
=========================== Full address ============================= Berwin A Turlach Tel.: +65 6516 4416 (secr) Dept of Statistics and Applied Probability +65 6516 6650 (self) Faculty of Science FAX : +65 6872 3919 National University of Singapore 6 Science Drive 2, Blk S16, Level 7 e-mail: statba at nus.edu.sg Singapore 117546 http://www.stat.nus.edu.sg/~statba
G'day all, On Fri, 9 Jan 2009 08:12:18 -0200 "Henrique Dallazuanna" <wwwhsd at gmail.com> wrote:
Try this also:
substr(basename(myfile), 1, nchar(basename(myfile)) - 4)
Or, in case that the extension has more than three letters or "myfile" is a vector of names: R> myfile <- "path1/path2/myoutput.txt" R> sapply(strsplit(basename(myfile),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" R> myfile2 <- c(myfile, "path2/path3/myoutput.temp") R> sapply(strsplit(basename(myfile2),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" R> myfile3 <- c(myfile2, "path4/path5/my.out.put.xls") R> sapply(strsplit(basename(myfile3),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" "my.out.put"
or have sub do the job for you:
filenames.ext = c("foo.bar", basename("foo/bar/hello.dolly"))
(filenames.noext = sub("[.][^.]*$", "", filenames.ext, perl=TRUE))
vQ
On Fri, Jan 9, 2009 at 6:52 AM, Wacek Kusnierczyk
Berwin A Turlach wrote:
G'day all, On Fri, 9 Jan 2009 08:12:18 -0200 "Henrique Dallazuanna" <wwwhsd at gmail.com> wrote:
Try this also: substr(basename(myfile), 1, nchar(basename(myfile)) - 4)
Or, in case that the extension has more than three letters or "myfile" is a vector of names: R> myfile <- "path1/path2/myoutput.txt" R> sapply(strsplit(basename(myfile),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" R> myfile2 <- c(myfile, "path2/path3/myoutput.temp") R> sapply(strsplit(basename(myfile2),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" R> myfile3 <- c(myfile2, "path4/path5/my.out.put.xls") R> sapply(strsplit(basename(myfile3),"\\."), function(x) paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" "my.out.put"
or have sub do the job for you:
filenames.ext = c("foo.bar", basename("foo/bar/hello.dolly"))
(filenames.noext = sub("[.][^.]*$", "", filenames.ext, perl=TRUE))
We can omit perl = TRUE here.
On Fri, Jan 9, 2009 at 6:52 AM, Wacek Kusnierczyk
or have sub do the job for you:
filenames.ext = c("foo.bar", basename("foo/bar/hello.dolly"))
(filenames.noext = sub("[.][^.]*$", "", filenames.ext, perl=TRUE))
We can omit perl = TRUE here.
or maybe not, depending on the actual task:
names = replicate(10000, paste(sample(c(letters, "."), 100,
replace=TRUE), collapse=""))
system.time(replicate(10, sub("[.][^.]*$", "", names, perl=TRUE)))
system.time(replicate(10, sub("[.][^.]*$", "", names)))
vQ
G'day Wacek, On Fri, 09 Jan 2009 12:52:46 +0100
Berwin A Turlach wrote:
G'day all, On Fri, 9 Jan 2009 08:12:18 -0200 "Henrique Dallazuanna" <wwwhsd at gmail.com> wrote:
Try this also:
substr(basename(myfile), 1, nchar(basename(myfile)) - 4)
Or, in case that the extension has more than three letters or "myfile" is a vector of names: R> myfile <- "path1/path2/myoutput.txt" R> sapply(strsplit(basename(myfile),"\\."), function(x) R> paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" R> myfile2 <- c(myfile, "path2/path3/myoutput.temp") R> sapply(strsplit(basename(myfile2),"\\."), function(x) R> paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" R> myfile3 <- c(myfile2, "path4/path5/my.out.put.xls") R> sapply(strsplit(basename(myfile3),"\\."), function(x) R> paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" "my.out.put"
or have sub do the job for you:
filenames.ext = c("foo.bar", basename("foo/bar/hello.dolly"))
(filenames.noext = sub("[.][^.]*$", "", filenames.ext, perl=TRUE))
Apparently also a possibility, I guess it can be made to work with the original example and my extensions. Though, it seems to require the knowledge of perl, or at least perl's regular expression. Cheers, Berwin
G'day Wacek,
Or, in case that the extension has more than three letters or
"myfile" is a vector of names:
R> myfile <- "path1/path2/myoutput.txt"
R> sapply(strsplit(basename(myfile),"\\."), function(x)
R> paste(x[1:(length(x)-1)], collapse="."))
[1] "myoutput"
R> myfile2 <- c(myfile, "path2/path3/myoutput.temp")
R> sapply(strsplit(basename(myfile2),"\\."), function(x)
R> paste(x[1:(length(x)-1)], collapse="."))
[1] "myoutput" "myoutput"
R> myfile3 <- c(myfile2, "path4/path5/my.out.put.xls")
R> sapply(strsplit(basename(myfile3),"\\."), function(x)
R> paste(x[1:(length(x)-1)], collapse="."))
[1] "myoutput" "myoutput" "my.out.put"
or have sub do the job for you:
filenames.ext = c("foo.bar", basename("foo/bar/hello.dolly"))
(filenames.noext = sub("[.][^.]*$", "", filenames.ext, perl=TRUE))
g'afternoon berwin,
Apparently also a possibility, I guess it can be made to work with the original example and my extensions.
i guess it does work with the original example and your extensions.
Though, it seems to require the knowledge of perl, or at least perl's regular expression.
oh my, sorry. it' so bad to go an inch out of the cosy world of r. but, as gabor pointed, 'perl=TRUE' is inessential here, so you actually need to know just (very basic) regular expressions, with no 'perl' implied. having learnt this simple regex syntax you can avoid the need for looking up strsplit and paste in tfm, so i'd consider it worthwhile. vQ
G'day Wacek, On Fri, 09 Jan 2009 14:22:19 +0100
Apparently also a possibility, I guess it can be made to work with the original example and my extensions.
i guess it does work with the original example and your extensions.
And I thought that you would have known for sure.....
Though, it seems to require the knowledge of perl, or at least perl's regular expression.
oh my, sorry. it' so bad to go an inch out of the cosy world of r.
Well, if that's how you feel, don't do it. I regularly use other languages besides R. Mostly C and Fortran, occasionally Python. But I never found time to learn Perl or Java or awk or C++ or....; some people do not have the time to learn all languages under the sun. Also, if one concentrates on a few, one can learn them really well.
but, as gabor pointed, 'perl=TRUE' is inessential here,
I thought that your answer to Gabor indicated that, depending on the context, perl=TRUE was essential; though I must admit that I did not run that code.
so you actually need to know just (very basic) regular expressions, with no 'perl' implied. having learnt this simple regex syntax you can avoid the need for looking up strsplit and paste in tfm, so i'd consider it worthwhile.
As people say, YMMV, I do not need to look up strsplit and/or paste; but I would have to look up what the regular expression syntax or finally memorise it; something I did not consider worthwhile so far. Cheers, Berwin
G'day Wacek, On Fri, 09 Jan 2009 12:52:46 +0100 Wacek Kusnierczyk <Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
Berwin A Turlach wrote:
G'day all, On Fri, 9 Jan 2009 08:12:18 -0200 "Henrique Dallazuanna" <wwwhsd at gmail.com> wrote:
Try this also: substr(basename(myfile), 1, nchar(basename(myfile)) - 4)
Or, in case that the extension has more than three letters or "myfile" is a vector of names: R> myfile <- "path1/path2/myoutput.txt" R> sapply(strsplit(basename(myfile),"\\."), function(x) R> paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" R> myfile2 <- c(myfile, "path2/path3/myoutput.temp") R> sapply(strsplit(basename(myfile2),"\\."), function(x) R> paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" R> myfile3 <- c(myfile2, "path4/path5/my.out.put.xls") R> sapply(strsplit(basename(myfile3),"\\."), function(x) R> paste(x[1:(length(x)-1)], collapse=".")) [1] "myoutput" "myoutput" "my.out.put"
using fixed = TRUE and not escaping '.' is slightly more efficient.
or have sub do the job for you:
filenames.ext = c("foo.bar", basename("foo/bar/hello.dolly"))
(filenames.noext = sub("[.][^.]*$", "", filenames.ext, perl=TRUE))
Apparently also a possibility, I guess it can be made to work with the original example and my extensions. Though, it seems to require the knowledge of perl, or at least perl's regular expression.
Actually, that's a valid regex in any of the variants offered. A more conventional writing of it is the second of
f <- 'foo.bar.R'
sub("[.][^.]*$", "", f)
[1] "foo.bar"
sub("\\.[^.]*$", "", f)
[1] "foo.bar"
It is the last that is used at various points in R's own code
(although sometimes with restrictions on what an 'extension' is, e.g.
sub("\\.[[:alnum:]]*$", "", f)
appears in the current SHLIB code.)
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
G'day Wacek, On Fri, 09 Jan 2009 14:22:19 +0100 Wacek Kusnierczyk <Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
Apparently also a possibility, I guess it can be made to work with
the original example and my extensions.
i guess it does work with the original example and your extensions.
And I thought that you would have known for sure.....
i thought i did until you made that comment, which made me think you've just discovered it doesn't.
Though, it seems to require the knowledge of perl, or at least
perl's regular expression.
oh my, sorry. it' so bad to go an inch out of the cosy world of r.
Well, if that's how you feel, don't do it.
quite the opposite.
I regularly use other languages besides R. Mostly C and Fortran, occasionally Python. But I never found time to learn Perl or Java or awk or C++ or....; some people do not have the time to learn all languages under the sun. Also, if one concentrates on a few, one can learn them really well.
i think i did not suggest the original poster to learn perl. many responses on this list involve regular expressions, and regexes are so ubiquitous in code that has to do with parsing and processing text, be it filenames or loads of data, that a user of r may well want to learn a bit of this stuff in addition to the details about how real numbers are represented below the surface. you may want to keep saying 'use r where applicable instead of worse tools', and i'd like to keep saying 'use regexes where they're applicable instead of worse tools'. same philosophy.
but, as gabor pointed, 'perl=TRUE' is inessential here,
I thought that your answer to Gabor indicated that, depending on the context, perl=TRUE was essential; though I must admit that I did not run that code.
i see i may have expressed that wrongly. it should have been "but maybe you'd want to keep it", meaning this is not essential for the final result, but may improve the runtime.
so you actually need to know just (very basic) regular expressions,
with no 'perl' implied. having learnt this simple regex syntax you
can avoid the need for looking up strsplit and paste in tfm, so i'd
consider it worthwhile.
As people say, YMMV, I do not need to look up strsplit and/or paste; but I would have to look up what the regular expression syntax or finally memorise it; something I did not consider worthwhile so far.
well, the regex syntax is fairly standard, though variations exist among languages. once you learn it, or rather the ideas behind the syntax, you're well equipped for quite a range of tasks. on the other hand, the details of strsplit and paste are pretty r-specific, and you don't gain much by remembering them (except for freeing yourself from having to read tfm again). i have seen quite a bunch of programs written by scientists who spent over one hundred lines of code on just parsing command line arguments; i wish they knew regexes exist (and better, getopt-like modules too). if you're doing serious programming without knowing regexes, you're rather lucky. vQ
Actually, that's a valid regex in any of the variants offered. A more conventional writing of it is the second of
f <- 'foo.bar.R'
sub("[.][^.]*$", "", f)
[1] "foo.bar"
sub("\\.[^.]*$", "", f)
[1] "foo.bar"
more conventional in r, perhaps. it's not portable, due to the 'escape the escape to have an escape' feature of r when it comes to regexes; in perl, for example, /\\.[^.]*$/ would hardly do the job. vQ
G'day Wacek, On Fri, 09 Jan 2009 15:19:46 +0100
i think i did not suggest the original poster to learn perl.
As I see it, you didn't suggest anything to the original poster, at least not directly. But, since these days you have to be subscribed to r-help to post IIRC, it is probably reasonable to assume that the original poster saw your posting.
many responses on this list involve regular expressions, and regexes are so ubiquitous in code that has to do with parsing and processing text, be it filenames or loads of data, that a user of r may well want to learn a bit of this stuff in addition to the details about how real numbers are represented below the surface.
You should really get rid of that chip on your shoulder.
you may want to keep saying 'use r where applicable instead of worse tools',
Now I am getting really confused, isn't your suggested solution not using R too? So why would I say something like this? I suggest you get rid of the chip on the other shoulder too... :)
well, the regex syntax is fairly standard, though variations exist among languages.
Exactly, and the existence of these variations which can trip one up and require to rtfm in anything but the most simplest situations, that's why regexp are not what jumps first to my mind.
i have seen quite a bunch of programs written by scientists who spent over one hundred lines of code on just parsing command line arguments; i wish they knew regexes exist (and better, getopt-like modules too). if you're doing serious programming without knowing regexes, you're rather lucky.
Probably depends on what one calls serious. Best wishes, Berwin
Dear all, The basename() function returns the extension also:
myfile <- "path1/path2/myoutput.txt" basename(myfile)
[1] "myoutput.txt" Is there any other function where it just returns plain base: "myoutput" i.e. without 'txt'
I'm curious about something: does "file extension" have a standard definition? Most (all? I haven't tried them all) of the solutions presented in this thread would return an empty string for the "plain base" if given the filename ".bashrc". Windows (where file extensions really mean something), though reluctant to create such a file, appears to agree that the extension is bashrc, even though to me it appears clear that that file has no extension. Duncan Murdoch
Hi,
[mailto:r-help-bounces at r-project.org] On Behalf Of Henrique Dallazuanna Try this also: substr(basename(myfile), 1, nchar(basename(myfile)) - 4)
This, of course, assumes that the extensions are always 3 characters.
Sometimes there might be more ("index.html"), sometimes less
("shellscript.sh").
Although my solution is not as compact as the others (I wish I was
proficient in 'mastering regular expressions'), I'd like to provide my
little code-snippet which does not require any regular expressions (but
expects a . in the filename).
######################
x1 <- "roland.txt"
x2 <- "roland.html"
x3 <- "roland.sh"
no.extension <- function(astring) {
if (substr(astring, nchar(astring), nchar(astring))==".") {
return(substr(astring, 1, nchar(astring)-1))
} else {
no.extension(substr(astring, 1, nchar(astring)-1))
}
}
no.extension(x1)
no.extension(x2)
no.extension(x3)
######################
Hope this helps a bit,
Roland
P.S. Any suggestions how to become more proficient with regular
expressions? The O'Reilly book ("Mastering...")? Whenever I tried
anything more complicated than basic usage (things like ^ $ * . ) in R,
I was way faster to write a new function (like above) instead of finding
a regex solution.
By the way: it might be still possible to *write* regular expressions,
but what about code re-use? Are there people who can easily *read*
complicated regular expressions?
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Hi,
[mailto:r-help-bounces at r-project.org] On Behalf Of Henrique Dallazuanna Try this also: substr(basename(myfile), 1, nchar(basename(myfile)) - 4)
This, of course, assumes that the extensions are always 3 characters.
The regex solutions posted did not make this assumption.
P.S. Any suggestions how to become more proficient with regular
expressions? The O'Reilly book ("Mastering...")? Whenever I tried
anything more complicated than basic usage (things like ^ $ * . ) in R,
I was way faster to write a new function (like above) instead of finding
a regex solution.
See the links in the Links box at: http://gsubfn.googlecode.com
By the way: it might be still possible to *write* regular expressions, but what about code re-use? Are there people who can easily *read* complicated regular expressions? ---------- This mail has been sent through the MPI for Demographic Research. Should you receive a mail that is apparently from a MPI user without this text displayed, then the address has most likely been faked. If you are uncertain about the validity of this message, please check the mail header or ask your system administrator for assistance.
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
On 1/8/2009 9:10 PM, Gundala Viswanath wrote:
Dear all, The basename() function returns the extension also:
myfile <- "path1/path2/myoutput.txt" basename(myfile)
[1] "myoutput.txt" Is there any other function where it just returns plain base: "myoutput" i.e. without 'txt'
I'm curious about something: does "file extension" have a standard definition? Most (all? I haven't tried them all) of the solutions presented in this thread would return an empty string for the "plain base" if given the filename ".bashrc". Windows (where file extensions really mean something), though reluctant to create such a file, appears to agree that the extension is bashrc, even though to me it appears clear that that file has no extension.
I'm not sure what is clear about it, but the GNU utility agrees with you:
basename abc/.exe .exe
.exe
basename abc/1.exe .exe
1 Anyone want to contribute code for an optional suffix= argument for R's basename()?
O__ ---- Peter Dalgaard ?ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
On 1/8/2009 9:10 PM, Gundala Viswanath wrote:
Dear all, The basename() function returns the extension also:
myfile <- "path1/path2/myoutput.txt" basename(myfile)
[1] "myoutput.txt" Is there any other function where it just returns plain base: "myoutput" i.e. without 'txt'
I'm curious about something: does "file extension" have a standard definition? Most (all? I haven't tried them all) of the solutions presented in this thread would return an empty string for the "plain base" if given the filename ".bashrc". Windows (where file extensions really mean something), though reluctant to create such a file, appears to agree that the extension is bashrc, even though to me it appears clear that that file has no extension.
Duncan, That is going to be highly OS and even OS version specific. More information here: http://en.wikipedia.org/wiki/Filename http://en.wikipedia.org/wiki/Filename_extension There are relevant standard extensions for standard file formats: http://en.wikipedia.org/wiki/List_of_file_formats but that does not guarantee that user created filenames will adhere to them, especially for text files. As you note, filenames beginning with a '.' will be common on Unixen/Linuxen as otherwise normally hidden system/config files. Such files would actually create problems if attempted to be opened on Windows with certain applications and I have even seen problems with such files when using SMB under Linux to access files on a server. HTH, Marc Schwartz
Duncan Murdoch wrote:
I'm curious about something: does "file extension" have a standard
definition? Most (all? I haven't tried them all) of the solutions
presented in this thread would return an empty string for the "plain
base" if given the filename ".bashrc".
right; there's a straightforward fix to my solution that accounts for
cases such as '.bashrc':
names = c("foo.bar", ".zee")
sub("(.+)[.][^.]+$", "\\1", names)
you could also use a lookbehind if possible (not in r, afaik).
vQ
P.S. Any suggestions how to become more proficient with regular
expressions? The O'Reilly book ("Mastering...")? Whenever I tried
anything more complicated than basic usage (things like ^ $ * . ) in R,
I was way faster to write a new function (like above) instead of finding
a regex solution.
the book you mention is good. you may also consider http://www.regular-expressions.info/ regexes are usually well explained with lots of examples in perl books.
By the way: it might be still possible to *write* regular expressions, but what about code re-use? Are there people who can easily *read* complicated regular expressions?
in some cases it is possible to write regular expressions in a way that facilitates reading them by a human. in perl, for example, you can use so-called readable regexes: / (.+) # match and remember at least one arbitrary character [.] # match a dot [^.]+ # match at least one non-dot character $ # end of string anchor /x; you can also use within regex comments: /(.+)(?# one or more chars)[.](?# a dot)[^.]+(?# one or more non-dots)$(?# end of string)/ nothing of the sorts in r, however. vQ
On Fri, Jan 9, 2009 at 4:20 PM, Wacek Kusnierczyk
Duncan Murdoch wrote:
I'm curious about something: does "file extension" have a standard definition? Most (all? I haven't tried them all) of the solutions presented in this thread would return an empty string for the "plain base" if given the filename ".bashrc".
right; there's a straightforward fix to my solution that accounts for
cases such as '.bashrc':
names = c("foo.bar", ".zee")
sub("(.+)[.][^.]+$", "\\1", names)
you could also use a lookbehind if possible (not in r, afaik).
or:
sub(".*[.]", ".", names)
[1] ".bar" ".zee"
On Fri, Jan 9, 2009 at 4:28 PM, Wacek Kusnierczyk
Rau, Roland wrote:
P.S. Any suggestions how to become more proficient with regular
expressions? The O'Reilly book ("Mastering...")? Whenever I tried
anything more complicated than basic usage (things like ^ $ * . ) in R,
I was way faster to write a new function (like above) instead of finding
a regex solution.
the book you mention is good. you may also consider http://www.regular-expressions.info/ regexes are usually well explained with lots of examples in perl books.
By the way: it might be still possible to *write* regular expressions, but what about code re-use? Are there people who can easily *read* complicated regular expressions?
in some cases it is possible to write regular expressions in a way that facilitates reading them by a human. in perl, for example, you can use so-called readable regexes: / (.+) # match and remember at least one arbitrary character [.] # match a dot [^.]+ # match at least one non-dot character $ # end of string anchor /x; you can also use within regex comments: /(.+)(?# one or more chars)[.](?# a dot)[^.]+(?# one or more non-dots)$(?# end of string)/ nothing of the sorts in r, however.
Supports that if you begin the regular expression with (?x) and use perl = TRUE. See ?regexp
On Fri, Jan 9, 2009 at 4:20 PM, Wacek Kusnierczyk
right; there's a straightforward fix to my solution that accounts for
cases such as '.bashrc':
names = c("foo.bar", ".zee")
sub("(.+)[.][^.]+$", "\\1", names)
you could also use a lookbehind if possible (not in r, afaik).
or:
sub(".*[.]", ".", names)
[1] ".bar" ".zee"
it was "foo" that was desired... vQ