25.10 Inline R Code

20200602 Often we find ourselves wanting to refer to the results of an R command within the text we are writing rather than as a separate code chunk. This is easily done using the Sexpr{} command in LaTeX.

To include today’s date within the narrative we can type the command sequence exactly as Sexpr{Sys.Date()}. This will be replaced with 2026-07-20 (assuming that is today). Any R function can be called in this way. To format the date, for example, we can use R’s base::format() function to specify how the date is displayed, so to produce we would use % Sexpr{Sys.Date() %>% format(format="%A, %e %B %Y")}.

We typically intermix a narrative of our dataset with output from R to support and illustrate the discussion. In the following sentence we do this showing first the output from the R command and then the actual R command we included in the source document. For example, the dataset from (G. Williams 2020) has 176,747 (i.e., \Sexpr{comma(nrow(weatherAUS))}) observations including observations of the following 4 of the ncol(weatherAUS) (i.e., \Sexpr{ncol(weatherAUS)}) available variables: MinTemp, MaxTemp, Rainfall, Evaporation. That list was generated using MinTemp, MaxTemp, Rainfall, Evaporation.

LaTeX treats some characters specially and we need to be careful to escape such characters. For example, the underscore ``_’’ is used to introduce a subscript in LaTeX. It needs to be escaped if we really want an underscore to be included in the compiled PDF document. If not LaTeX will likely complain. As an example we might list one of the variable names from the dataset with an underscore in its name: RISK_MM (\Sexpr{names(weatherAUS)[23]}). We will see an error like:

KnitR.tex:230: Missing $ inserted.
KnitR.tex:230: leading text: ...an underscore in its name: RISK_
KnitR.tex:232: Missing $ inserted.

(Harrell 2021) provides Hmisc::latexTranslate() to assist here. It was used above to print the variable name: Sexpr{latexTranslate(names(weatherAUS)[23])}. There are other support functions in Hmisc (Harrell 2021) that are useful when working with knitr (Xie 2021) and LaTeX—see library(help=Hmisc) for further information.

References

Harrell, Frank E, Jr. 2021. Hmisc: Harrell Miscellaneous. https://CRAN.R-project.org/package=Hmisc.
Williams, Graham. 2020. Rattle: Graphical User Interface for Data Science in r. https://rattle.togaware.com/.
———. 2021. Knitr: A General-Purpose Package for Dynamic Report Generation in r. https://yihui.org/knitr/.


Your donation will support ongoing development and give you access to the PDF version of this book. Desktop Survival Guides include Data Science, GNU/Linux, and MLHub. Books available on Amazon include Data Mining with Rattle and Essentials of Data Science. Popular open source software includes rattle, wajig, and mlhub. Hosted by Togaware, a pioneer of free and open source software since 1984.
Copyright © 1995-2021 Graham.Williams@togaware.com Creative Commons Attribution-ShareAlike 4.0.