06. Latex Output

In This Vignette

What is Latex?
Example Pivot Table
Rendering a Pivot Table in Latex
Rendering a Pivot Table to PDF via R Markdown
Styling a Pivot Table in Latex
Rendering part of a Pivot Table
Further Reading

What is Latex?

Latex is used to write documents. Latex documents are written in plain-text that contains tags for defining the structure and formatting of the document, i.e. a different approach compared to typical WYSIWYG document editors like Microsoft Word. Latex is widely used in academia for the publishing of scientific papers.

A trivial example of a Latex document is:

\documentclass{article}
\begin{document}
Hello World!
\end{document}

For more information see Wikipedia or Latex-Tutorial.com.

A helpful reference for understanding the structure of Latex pivot tables can be found on wikibooks.

Example Pivot Table

The following pivot table is used as the basis of the examples in the rest of this vignette:

library(pivottabler)
pt <- PivotTable$new()
pt$addData(bhmtrains)
pt$addColumnDataGroups("TrainCategory")
pt$addRowDataGroups("TOC")
pt$defineCalculation(calculationName="TotalTrains", summariseExpression="n()")
pt$renderPivot()

Rendering a Pivot Table in Latex

A pivottabler pivot table can be output in Latex using the pt$getLatex() function. The Latex for the example pivot table above is:

library(pivottabler)
pt <- PivotTable$new()
pt$addData(bhmtrains)
pt$addColumnDataGroups("TrainCategory")
pt$addRowDataGroups("TOC")
pt$defineCalculation(calculationName="TotalTrains", summariseExpression="n()")
cat(pt$getLatex())

\begin{table}[h!]
  \centering
  \begin{tabular}{|l|rrr|}
    \hline
    & Express Passenger & Ordinary Passenger & Total\\
    \hline
    Arriva Trains Wales  & 3079 & 830 & 3909\\
    CrossCountry  & 22865 & 63 & 22928\\
    London Midland  & 14487 & 33792 & 48279\\
    Virgin Trains  & 8594 &  & 8594\\
    Total  & 49025 & 34685 & 83710\\
    \hline
  \end{tabular}
\end{table}

The caption for the table can be specified using the caption argument when calling the pt$getLatex() function. The table label, used to cross-reference the table in other parts of the document, can be specified using the label argument. Both of these arguments are illustrated in the examples later in this vignette.

The equivalent quick-pivot command for the example pivot table shown above is:

library(pivottabler)
cat(qlpvt(bhmtrains, "TOC", "TrainCategory", c("TotalTrains"="n()")))

More information on the quick-pivot functions can be found in the Introduction vignette.

Rendering a Pivot Table to PDF via R Markdown

R Markdown can be used to create PDF documents. R Markdown is compiled to a PDF document using the knitr package and pandoc, via Latex. This allows the pt$getLatex() function to be used with R Markdown to generate tables in PDF documents.

The multirow latex package is used to allow table cells to span multiple rows. Note the header-include in the R Markdown example below.

A minimal example using an R Markdown file:

Minimal R Markdown Example

When the PDF is generated, the resulting table appears as:

Resulting Output

When multiple row/column groups are present, additional lines are drawn within the table:

Larger Output

Styling a Pivot Table in Latex

Styling Latex has a great many differences compared to styling HTML. Therefore the HTML-based approaches to styling a pivottabler pivot table, as described in the Styling vignette, do not apply to tables generated in Latex.

A couple of basic options for styling the pivot table headers are offered, controlled by setting either/both of the boldHeadings and/or italicHeadings arguments to TRUE when calling pt$getLatex(). For example, specifying italicHeadings=TRUE:

Italic Headings

Rendering part of a Pivot Table

Pivot tables can easily grow to be larger than the height/width of a single A4 page. To split a pivot table across multiple pages, the following arguments can be specified when calling pt$getLatex():

fromRow
toRow
fromColumn
toColumn

Integer numbers should be specified for these arguments. The numbers are 1-based and specify the cells in the body of the pivot table only, i.e. they do not include either the row/column headings. In the example pivot table above:

the Arriva Trains Wales, Express Passenger cell with value 3079 is at row 1, column 1.
the London Midland, Ordinary Passenger cell with value 33792 is at row 3, column 2.
the Total, Total cell with value 83710 is at row 5, column 3.

Chris Bailiss

2023-10-01