How to cross-reference an equation in an R help file/roxygen2

Question

I'm in the process of documenting some of my functions for an R package I'm making.

I'm using roxygen markup, though that is largely irrelevant to my question.

I have put equations into my documentation using \deqn{...}. My question is: Is there a way to cross-reference this equation later on?

For example, in my Rd file:

\deqn{\label{test}
 y = mx + b
}

Can I later do something like:

Referring to equation \ref{test}, ...

I've tried \eqref{test}, \ref{test} (which both get "unknown macro" and don't get linked ), and also \link{test} (which complains it can't find function test because it's really just for linking to other functions).

Otherwise I fear I may have to do something hacky and add in the -- (1) and Refer to equation (1) manually within the \deqn etc in the Rd file...

Update

General answer appears to be "no". (awww...)

However, I can write a vignette and use "normal" latex/packages there. In any case, I've just noticed that the matrix equations I spent ages putting into my roxygen/Rd file look awful in the ?myFunction version of the help (they show up as just-about literal latex source). Which is a shame, because they look beautiful in the pdf version of the help.

@Iterator has pointed out the existence of conditional text, so I'll do ASCII maths in the .Rd files, but Latex maths in the pdf manual/vignette.

Answer 1

I'm compiling my comments above into an answer, for the benefit of others.

First, I do not actually know whether or not .Rd supports tagging of equations. However, the .Rd format is such a strict subset of LaTeX, and produces very primitive text output, that shoehorning extensive equations into its format could be a painful undertaking without much benefit to the user.

The alternative is to use package vignettes, or even externally hosted documentation (as is done by Hadley Wickham, for some of his packages). This will allow you to use PDFs or other documentation, to your heart's content. In this way, you can include screenshots, plots, all of the funkiest LaTeX extensions that only you have, and, most significantly, the AMS extensions that we all know and love.

Nonetheless, one can specify different rendering of a given section of documentation (in .Rd) based on the interface, such as text for the console, nice characters for HTML, etc., and conditional text supports that kind of format variation.

It's a good question. I don't know the answer regarding feasibility, but I had similar questions about documenting functions and equations together, and this investigation into what's feasible with .Rd files has convinced me to use PDF vignettes rather than .Rd files.