In parsermd: Formal Parser and Related Tools for R Markdown Documents

Wrap long lines

Long lines in the output will not be (hard-)wrapped automatically unless you break them manually.

a <- '## "stx2A; shiga-like toxin II A subunit encoded by bacteriophage BP-933W; K11006 shiga toxin subunit A" '
a

Perhaps you see it is wrapped in RStudio, but that is because <pre> has the CSS attribute white-space: pre-wrap;. For LaTeX output, the output is in the verbatim environment by default, which will not wrap long lines (everything is shown as is).

You can redefine the output hook function so that you can instruct some chunks to hard-wrap their output lines, e.g.

library(knitr)
hook_output = knit_hooks$get('output')
knit_hooks$set(output = function(x, options) {
  # this hook is used only when the linewidth option is not NULL
  if (!is.null(n <- options$linewidth)) {
    x = knitr:::split_lines(x)
    # any lines wider than n should be wrapped
    if (any(nchar(x) > n)) x = strwrap(x, width = n)
    x = paste(x, collapse = '\n')
  }
  hook_output(x, options)
})

Now see the output of a (note linewidth is not a default knitr option):

a

parsermd documentation built on May 20, 2021, 5:08 p.m.