I am wondering it there exists a method to link to function from other package when I\'m trying to write a documentation for new package using roxygen2
In addition to the answer by potockan:
Some packages document several functions in a single help page. For example, the trim function from Bioconductor package GenomicRanges is documented in intra-range-methods (which is also the name of a help page from other packages such as IRanges).
To link to the right page with roxygen2 you can use:
\link[GenomicRanges:intra-range-methods]{trim}
or
\code{\link[GenomicRanges:intra-range-methods]{trim}}
to format the text correctly.
The help page will only show trim but will link to the right help page.