How to use escape characters in a string

Please read R FAQ 7.37.

You need to escape the backslash:

z<- as.character("`X^`R\\`S")
z

[1] "`X^`R\\`S"

cat(z)

`X^`R\`S

Bert Gunter
Genentech Nonclinical Statistics


-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of mary guo
Sent: Friday, January 29, 2010 1:58 PM
To: r-help at r-project.org
Subject: [R] How to use escape characters in a string

Hi,
I want to use a character as below in R,

 as.character("`X^`R\`S")
[1] "`X^`R`S"
Warning messages:
1: '\`' is an unrecognized escape in a character string
2: unrecognized escape removed from "`X^`R\`S"

But I found errors.
Can I use some option in as.character() to change this?

Thanks

Mary


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Hi,
I want to use a character as below in R,

What character?

as.character("`X^`R\`S")
[1] "`X^`R`S"
Warning messages:
1: '\`' is an unrecognized escape in a character string
2: unrecognized escape removed from "`X^`R\`S"

> nchar("`X^`R\`S")
[1] 7
Warning messages:
1: '\`' is an unrecognized escape in a character string
2: unrecognized escape removed from "`X^`R\`S"
 > substr("`X^`R\`S" , 7,7)
[1] "S"
Warning messages:
1: '\`' is an unrecognized escape in a character string
2: unrecognized escape removed from "`X^`R\`S"
 > substr("`X^`R\`S" , 6,6)
[1] "`"
Warning messages:
1: '\`' is an unrecognized escape in a character string
2: unrecognized escape removed from "`X^`R\`S"
 > substr("`X^`R\`S" , 5,5)
[1] "R"

But I found errors.
Can I use some option in as.character() to change this?

What do you want? Just to add a back-slash?

 > nchar("`X^`R\\`S")
[1] 8
 > substr("`X^`R\\`S" , 6,6)
[1] "\\"
Notice that one of the backslashes is not counted because it is not  
present in the internal representation. It is, however, printed with  
doubling.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT