I'm using roxygen2 for my package description and I want to have mathematic equations in my documentation. For example I want to write n_{u} like a formula. When I write \eqn{n_{u}} in @details nothing happens but the text is italic. I document the package with control, shift and d and then i push "Clean and rebuild". Did I forget anything?
This is expected behaviour. The R documentation format doesn't have "real" equations like you might get from Mathjax or another fully-fledged Latex engine; it uses a basic representation that just copies your equation text but sets it in italics. Think of it as more akin to code, rather than mathematical notation.