What documentation exists for R?
What documentation exists for R?
What documentation exists for R?
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Chapter 7: R Miscellanea 90<br />
quote at either end, but there are strings that cannot be represented that way, e.g., strings<br />
that themselves contains the quote character. So<br />
> str str<br />
[1] "This \"text\" is quoted"<br />
> cat(str, "\n")<br />
This "text" is quoted<br />
The escape sequences ‘\"’ and ‘\n’ represent a double quote and the newline character<br />
respectively. Printing text strings, using print() or by typing the name at the prompt will<br />
use the escape sequences too, but the cat() function will display the string as-is. Notice<br />
that ‘"\n"’ is a one-character string, not two; the backslash is not actually in the string, it<br />
is just generated in the printed representation.<br />
> nchar("\n")<br />
[1] 1<br />
> substring("\n", 1, 1)<br />
[1] "\n"<br />
So how do you put a backslash in a string? For this, you have to escape the escape<br />
character. I.e., you have to double the backslash. as in<br />
> cat("\\n", "\n")<br />
\n<br />
Some functions, particularly those involving regular expression matching, themselves use<br />
metacharacters, which may need to be escaped by the backslash mechanism. In those cases<br />
you may need a quadruple backslash to represent a single literal one.<br />
In current versions of R (up to 2.4.0) an unknown escape sequence like ‘\p’ is quietly<br />
interpreted as just ‘p’. The development version now emits a warning.
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