On Apr 24, 2006, at 10:23 AM, Torsten Hothorn wrote:
>
> Dear developeRs,
>
> I thought that backslashes can be escaped in the usual way (and I
> think I
> did this before) but I can't see why
>
> R> gsub("\\", "x", "\alpha")
> Error in gsub(pattern, replacement, x, ignore.case, extended, fixed,
> useBytes) :
> invalid regular expression '\'
>
> gives an error. Or am I just blind?
>
In REs you need to escape backslashes, so you need double-escaping:
one for the R string representation and one for the RE:
> gsub("\\\\", "x", "\\alpha")
[1] "xalpha"
For illustration purposes:
> cat("\\\\")
\\
> cat("\alpha")
lpha
> cat("\\alpha")
\alpha
Cheers,
Simon
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