Question

Is there a nice way to extract get the R-help page from an installed package in the form of an R object (e.g a list). I would like to expose help pages in the form of standardized JSON or XML schemas. However getting the R-help info from the DB is harder than I thought.

I hacked together a while ago to get the HTML of an R help manual page. However I would rather have a general R object that contains this information, that I can render to JSON/XML/HTML, etc. I looked into the helpr package from Hadley, but this seems to be a bit of overkill for my purpose.

Answer 1

So below what I hacked together. However I yet have to test it on many help files to see if it generally works.

Rd2list <- function(Rd){
    names(Rd) <- substring(sapply(Rd, attr, "Rd_tag"),2);
    temp_args <- Rd$arguments;

    Rd$arguments <- NULL;
    myrd <- lapply(Rd, unlist);
    myrd <- lapply(myrd, paste, collapse="");

    temp_args <- temp_args[sapply(temp_args , attr, "Rd_tag") == "\\item"];
    temp_args <- lapply(temp_args, lapply, paste, collapse="");
    temp_args <- lapply(temp_args, "names<-", c("arg", "description"));
    myrd$arguments <- temp_args;
    return(myrd);
}

getHelpList <- function(...){
    thefile <- help(...)
    myrd <- utils:::.getHelpFile(thefile);
    Rd2list(myrd);
}

And then you would do something like:

myhelp <- getHelpList("qplot", package="ggplot2");
cat(jsonlite::toJSON(myhelp));