[R] Difficulty with "\\" in string functions....

[William Dunlap]

You can also avoid the issue by using the basename and dirname functions.

> Fname1 <- "D:\\Data\\OneDrive\\ISTA Documents\\QT_App\\QT Analysis Input
Data Example WorkBook.xlsx"
> basename(Fname1)
[1] "QT Analysis Input Data Example WorkBook.xlsx"
> dirname(Fname1)
[1] "D:/Data/OneDrive/ISTA Documents/QT_App"

Use normalizePath if you need to convert those / to \ on Windows.

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Mon, Feb 11, 2019 at 12:26 PM Bernard McGarvey <
mcgarvey.bernard using comcast.net> wrote:

> Brilliant! Thanks a million Ivan.
>
> Lion Bernard McGarvey
>
>
> Director, Fort Myers Beach Lions Foundation, Inc.
>
>
> Retired (Lilly Engineering Fellow).
>
>
> > On February 11, 2019 at 3:13 PM Ivan Krylov <krylov.r00t using gmail.com>
> wrote:
> >
> >
> > On Mon, 11 Feb 2019 15:01:16 -0500 (EST)
> > Bernard McGarvey <mcgarvey.bernard using comcast.net> wrote:
> >
> > > Now I try to split it using
> > >
> > >
> > > str_split(Fname1,"\\")
> > >
> > >
> > > but this returns an error
> > >
> > >
> > > Error in stri_split_regex(string, pattern, n = n, simplify =
> > > simplify, : Unrecognized backslash escape sequence in pattern.
> > > (U_REGEX_BAD_ESCAPE_SEQUENCE)
> >
> > This happens because the second parameter of str_split is by default a
> > regular expression, and a backslash has a special meaning in regular
> > expressions: when preceding other characters, it may change the way
> > they are interpreted. (For example, w means a literal "w"
> > character, while \w means "any alphanumeric character". On the
> > other hand, [ starts a character group, but \[ means just an opening
> > square bracket.) See ?regex for more info on that.
> >
> > Since you want a literal backslash, you need to escape it with another
> > backslash: \\
> >
> > But to write a string literal of a double-backslash in R, you need to
> > escape both backslash characters, each with their own backslash: "\\\\"
> >
> > ## fname <- "D:\\Data\\OneDrive\\ISTA Documents\\QT_App\\QT Analysis
> > Input Data Example WorkBook.xlsx"
> > ## message("\\\\")
> > \\
> > ## str_split(fname, "\\\\")
> > [[1]]
> > [1] "D:"
> > [2] "Data"
> > [3] "OneDrive"
> > [4] "ISTA Documents"
> > [5] "QT_App"
> > [6] "QT AnalysisInput Data Example WorkBook.xlsx"
> >
> > You can also avoid all layers of the backslash hell (except the first)
> > if you choose to split by fixed strings instead of regular expressions
> > by using stringr::fixed:
> >
> > ## str_split(fname, fixed("\\"))
> >
> > --
> > Best regards,
> > Ivan
>
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