knitr (version 1.1)

set_header: Set the header information

Description

Some output documents may need appropriate header information, for example, for LaTeX output, we need to write \usepackage{tikz} into the preamble if we use tikz graphics; this function sets the header information to be written into the output.

Usage

set_header(...)

Arguments

...

the header components; currently possible components are highlight, tikz and framed, which contain the necessary commands to be used in the HTML header or LaTeX preamble; note HTML output only uses the

Value

• The header vector in opts_knit is set.

Details

By default, knitr will set up the header automatically. For example, if the tikz device is used, knitr will add \usepackage{tikz} to the LaTeX preamble, and this is done by setting the header component tikz to be a character string: set_header(tikz = '\usepackage{tikz}'). Similary, when we highlight R code using the highlight package (i.e. the chunk option highlight = TRUE), knitr will set the highlight component of the header vector automatically; if the output type is HTML, this component will be different -- instead of LaTeX commands, it contains CSS definitions.

For power users, all the components can be modified to adapt to a customized type of output. For instance, we can change highlight to LaTeX definitions of the listings package (and modify the output hooks accordingly), so we can decorate R code using the listings package.

Examples

set_header(tikz = "\\usepackage{tikz}")
opts_knit$get("header")