Data Science Desktop Survival Guide by Graham Williams
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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 Wednesday, 20 July 2026 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 weatherAUS dataset from rattle has 176,747 (i.e., \Sexpr{comma(nrow(weatherAUS))}) observations including observations of the following 4 of the 24 (i.e., \Sexpr{ncol(weatherAUS)}) available variables: MinTemp, MaxTemp, Rainfall, Evaporation. That list was generated using \Sexpr{names(weatherAUS)[3:6] %>% paste(collapse=", ")}.

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 weatherAUS 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.

Hmisc 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 that are useful when working with knitr and LaTeX—see library(help=Hmisc) for further information.