Get a help page as an Rd object from an installed or source package.

## Usage

Rdo_fetch(Rd_name = character(0), package, dir = ".", installed = TRUE)

## Arguments

Rd_name

names of one or more Rd help pages. name here is the name of an Rd file stripped from the extension.

package

the package from which to get the Rd object, a character string.

dir

a character string giving the root directory of a source package. Used only if package is missing.

installed

if TRUE, the default, the Rd object is taken unconditionally from the installed package. If FALSE, the help page may be taken from a source tree, if appropriate (typically if package is in developer's mode under devtools, see Details).

## Details

If Rd_name is a character string (typical use case), the corresponding help page is returned as an object from class "Rd". If the length of Rd_name is greater than one, the result is a Rd_named list containing the corresponding "Rd" objects. The default Rd_name = character(0) requests all Rd pages in the package.

Note that Rd_name does not contain the extention ".Rd" but the names in the returned list do.

Argument package names the package from which to fetch the documentation object. With the default installed = TRUE the object is taken unconditionally from the installed package. To get it from the source tree of a package, use argument "dir" instead. The default, "", for dir is suitable for workflows where the working directory is the root of the desired package.

Argument installed concerns primarily development under package "devtools". "devtools" intercepts and modifies several base R commands, concerning access to system files and getting help, with the aim of rerouting them to the source trees of packages under developer's mode. If argument installed is TRUE, the default, the requested pages are taken from the installed package, even if it is in development mode. If argument installed is FALSE, the Rd objects are taken from the corresponding source tree, if the specified package is under developer's mode, and from the installed package otherwise.

Argument Rd_name is the name used in the \name section of Rd files.

When working off the source tree of a package, Rdo_fetch processes the Rd files, so roxygen2 users need to update them if necessary.

## Value

if length(Rd_name) = 1, an object of class "Rd", otherwise a list of "Rd" objects.

## Author

Georgi N. Boshnakov

## Examples

## get a single help page
rdo <- Rdo_fetch("viewRd", package = "Rdpack")
Rdo_show(rdo)

## get a list of help pages
rdo <- Rdo_fetch(c("viewRd", "reprompt"), package = "Rdpack")
names(rdo)
#> [1] "viewRd.Rd"   "reprompt.Rd"
`