Adding a single backslash (\) to a string in R

Question

I am working on knitr right now, One of the string that I was trying to print has the % symbol. I read up on the TeX manual that to a print the % symbol. TeX should have the string as \% to display the code.

Using the command gsub I tried to do the following:

try = "0% success"
try2 = gsub("%","\%",try,fixed = TRUE)

gsub throws an invalid escape character error

If I do this:

try = "0% success"
try2 = gsub("%","\\\\%",try,fixed = TRUE)

knitr will still not be able to print the string

Please suggest me with a way that I can solve my problem

--------EDIT------------------

I want the string in try to displayed as it is in my output PDF I am using this in knitr as \textit{\Sexpr{try}} When the tex file gets created, it believes that the text after percentage is a comment. I am creating an rnw file first and then creating the tex file, after which using texi2pdf to get the pdf file

----EDIT 2 -------------

I am not very good with either knitr or LaTeX

Could you please elaborate your workflow? Are we to understand that these commands are to be included in a knitr chunk? What is the desired output in LaTeX? — Maxim.K
– Maxim.K, Commented Dec 27, 2013 at 12:27
I want the string to be displayed as it is, my output pdf that I am generating should have the string "0% success" printed the way it is. But when knitr encounters the % it believes the string to be a comment, I am using this in knitr as \textit{\Sexpr{try}} — Mayank Bansal
– Mayank Bansal, Commented Dec 27, 2013 at 12:30
You still haven't clarified. There are many paths from Knitr to LaTeX. Is it via Rmd? Or Rnw? Are you having problems echoing R commands in the PDF? Or are you trying to create LaTeX code with an R function? When I plug your code in knitr, I have no issues displaying % in PDF. I knit an MD file, and the resulting .tex gives \begin{verbatim} try = "0% success" try \end{verbatim} \begin{verbatim} [1] "0% success" \end{verbatim} — Maxim.K
– Maxim.K, Commented Dec 27, 2013 at 12:35
Sorry, I did not understand initially what you asked for.. I am creating an rnw file, then creating the tex. The texi2pdf operation is not able to print it. — Mayank Bansal
– Mayank Bansal, Commented Dec 27, 2013 at 12:39
So basically you want to create a variable in R (containing "0% success") and then render it in the string \textit{\Sexpr{try}}, where try is that variable in R? — Maxim.K
– Maxim.K, Commented Dec 27, 2013 at 12:43

LPH · Accepted Answer · 2013-12-27 12:35:14Z

11

why are you jumping fomr one "\" to 4 "\"?

> try2 = gsub("%","\\%",try,fixed = TRUE)
> try2
[1] "0\\% success"

This should be read as "\\", which (as far as i know) the regular expression will understand as an "\".

I hope i understood you right- and this is a possible sulution for you!

answered Dec 27, 2013 at 12:35

LPH

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3 Comments

Mayank Bansal Over a year ago

No, texi2pdf operation still thinks of the string after the % operation as a comment and gives me an error in that process because of that.

LPH Over a year ago

oh, sorry! Now i can see your problem- but i can´t reproduce it;

Mayank Bansal Over a year ago

You were right, so If I put two // and output from R. It does come out perfectly, sorry my bad

Maxim.K · Accepted Answer · 2013-12-27 12:54:42Z

5

You need two backslashes to escape:

<<>>=
try = "0\\% success"
@

Some text in LaTex \Sexpr{try}.

After knitting the document one obtains the following LaTeX code:

\begin{document}

\begin{knitrout}
\definecolor{shadecolor}{rgb}{0.969, 0.969, 0.969}\color{fgcolor}\begin{kframe}
\begin{alltt}
\hlstd{try} \hlkwb{=} \hlstr{"0\textbackslash{}\textbackslash{}% success"}
\end{alltt}
\end{kframe}
\end{knitrout}

Some text 0\% success

\end{document}

This, of course, assuming echo=TRUE.

edited Dec 27, 2013 at 12:54

answered Dec 27, 2013 at 12:49

Maxim.K

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3 Comments

Scott Ritchie Over a year ago

This still causes the problem? You can see its being knitd to \textbackslash{}\textbackslash{}% instead of the desired \%

Maxim.K Over a year ago

I can see that, but that is contained within the knitrout environment. I have used the PDF compiler which is provided in R studio internally, as well as TeX Studio to confirm the generalizability. Both conversions gave me the required PDF. For your convenience I've included all three files in a zip dl.dropboxusercontent.com/u/18527706/stack.zip

Scott Ritchie Over a year ago

Ah I'm not familiar with the knitrout environment. I didn't see that it had compiled the Some text 0\% success as well!

Enrique Pérez Herrero · Accepted Answer · 2023-07-12 19:08:50Z

0

Other way to solve this issue is to use raw strings:

try = "0% success"
try2 = gsub(r"(%)", r"(\%)", try, fixed = TRUE)
try2
#[1] "0\\% success"

answered Jul 12, 2023 at 19:08

Enrique Pérez Herrero

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