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In R you can search the documentation by typing a question mark ? or a double question mark ??. How do you search the manual for strings in the Julia REPL?

>?first
No documentation for ‘first’ in specified packages and libraries:
you could try ‘??first’

>??first

In the R console a browser window opens up:

enter image description here

In RStudio the page is opened within the IDE.

The help() function and ? help operator in R provide access to the documentation pages for R functions, data sets, and other objects, both for packages in the standard R distribution and for contributed packages.

The help() function and ? operator are useful only if you already know the name of the function that you wish to use. Other ways to search include apropos and ??

The apropos() function searches for objects, including functions, directly accessible in the current R session that have names that include a specified character string.

The ?? operator is a synonym for help.search(). The help.search() function scans the documentation for packages installed in your library. The argument to help.search() is a character string or regular expression.

P.S. I intend to answer my own question.

GuedesBF
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PatrickT
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    Does R's `??` search _all_ packages in CRAN or just the loaded ones? – mbauman May 14 '21 at 14:14
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    @mbauman It seems `?` searches for _loaded_ packages, while `??` searches for _installed_ packages: "The help.search() function scans the documentation for packages installed in your library." and "The ?? operator is a synonym for help.search()" (from the OP link) Any case, not from the whole CRAN... – Antonello May 14 '21 at 14:41
  • Thanks for these clarifications. I really only ever used `?` and `??` and never noticed the difference between `loaded` and `installed`, but that's actually a very important one! – PatrickT May 14 '21 at 20:57

1 Answers1

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Julia has similar interactive utilties. Julia's main search utility for docstrings is named apropos.

To search the documentation for information about "first" in Julia, you have apropos("first") or equivalently ?"first". Thus ?"first" is roughly equivalent to R's ??.

To search for functions and methods, you can type a singe question mark ?, just as with R. In the Julia REPL, as you type the question mark, the prompt changes to a question mark. If you type "first" it searches through strings, while if you type first without quote-marks, you get a search over variables exported by the modules currently loaded.

Illustration:

help?>"first"  

# or equivalently:

julia>apropos("first")

enter image description here

help?>first

enter image description here

If you search for a string, case is ignored. If you want to search within the DataFrames module, type using DataFrames before searching.

This also works in Visual Studio Code and Atom:

enter image description here

PatrickT
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  • I thought `appropos` just lists all the functions which has the word `first` in them. That's both in `Julia` and `R`.(Note that there is `appropos` in both R and Julia). I perceive OP is asking with regards to help page. – Onyambu May 14 '21 at 01:54
  • Well, `apropos` in Julia corresponds to `apropos` in R. so still I do not see how this fits the answer to `??` for Julia – Onyambu May 14 '21 at 02:01
  • There is also `??` in Julia, BTW. It's for "Extended help" which, in some docstrings, is more examples etc. – mcabbott May 14 '21 at 02:16
  • @mcabbott, I didn't know that. How do you use `??` in Julia? And where is the documentation? Feel free to post an answer! Thanks. – PatrickT May 14 '21 at 02:18
  • Extended help was introduced in Julia 1.5. Do it like this: `help?> ?first` (the first question mark moves you to the help prompt, the second one is a literal prefix on the name). – mbauman May 14 '21 at 14:59
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    Thanks @mbauman, Well for me `?` followed by `first` gives the same result as `?` followed by `?first`, so I couldn't tell there was a difference. Also it's not a string search like `??` does in `R`, am I understanding correctly? – PatrickT May 14 '21 at 21:02