Question

Why does nchar("\\")=1, nchar("\abcde")=5 etc. in R ? Which function use to have nchar("\\")=2, nchar("\abcde")=6 ?

Answer 1

In R, if you want a literal \, you need to escape it as other’s have said. I don’t see the reason for encodeString() in your examples. It is easier to just use nchar() and remember the first line of my Answer: escape your \

> nchar("\\\\")
[1] 2
> nchar("\\abcde")
[1] 6

If you want to forget about the escape then encodeString() can help, but you either do one (escape them manually) or use escapeString(), not both:

> encodeString("\\")
[1] "\\\\"
> encodeString("\abcde")
[1] "\\abcde"

Finally, \uXXXX is a way of entering a unicode characters in R and this catches out encodeString():

> nchar(encodeString("\u2642"))
[1] 1

as it wants to treat this as a representation of a unicode character. In this case, the “escape them yourself” thing does the right thing:

> nchar("\\u2642")
[1] 6

I’m not sure of a straight forward way to replace \ with \\ in R where the string is a \uXXXX as that will get interpreted first to the unicdoe character and only then will the replacement take place (but at that point there are no \. See ?Quotes for a list of the escape sequences used in R.