On-demand installation of packages

Question

Is there a "standard" way to load a package, and install it if it isn't installed yet? Something like

if (!is.installed(package))
    install(package)
library(package)

(pseudocode!), encapsulated in a neat function?

I'm usually having a hard time after wiping my private site library, which I do every now and then. If my scripts all used this "install-on-demand" facility, this would just happen automatically.

I use what you suggest with `is.installed <- function(mypkg) is.element(mypkg, installed.packages()[,1])`. Of course, I set `dependencies=TRUE`. — Roland, Nov 07 '13 at 14:23
I do this: http://stackoverflow.com/questions/19596359/install-package-library-if-not-installed/19598076#19598076 — Alex Vorobiev, Nov 07 '13 at 14:54

Tyler Rinker · Answer 1 · 2015-02-15T02:09:20.153

2

Dason K. and I have a package in the works on GitHub that needs some testing and a bit of cleaning and eventually will be pushed to CRAN. The function p_load in the package does this.

library(devtools)
install_github("trinker/pacman")

edited Feb 15 '15 at 02:09

answered Nov 07 '13 at 18:57

Tyler Rinker

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Thanks! Why don't you rather answer the linked question, now this is an official dupe? Also, how does `pacman` compare with [`packrat`](https://github.com/rstudio/packrat) and [`rbundler`](https://github.com/opower/rbundler)? – krlmlr Nov 07 '13 at 20:55
*bump* Why don't you re-post it here, where it might get more attention: http://stackoverflow.com/questions/4090169/elegant-way-to-check-for-missing-packages-and-install-them?lq=1 – krlmlr Nov 09 '13 at 07:17
@krlmlr **pacman** does very different things than **packrat**. The former works to improve workflow through more consistently named and compact acting functions while the later seems to be more focused on preserving a particular environment, both useful for different purposes. – Tyler Rinker Feb 15 '15 at 02:12

IRTFM · Answer 2 · 2013-11-07T22:04:23.273

I see that other answers have been given but my preference would be:

 if ( !require('pkg') ) { install.packages('pkg', dependencies=TRUE);
                        require('pkg') }

If you want to suppress the warning, then add quietly=TRUE to the first require call. I suppose you could bundle this into a function, called, what? insist?

 insist <- function(pkg){
          if ( !require(pkg, character.only=TRUE) ) { 
                    install.packages(as.character(pkg), dependencies=TRUE)
          require(pkg, character.only=TRUE) }
                         }

(My major stumbling block: The first argument to require didn't seem to get evaluated unless character.only=TRUE. Took me several reads of the ?require page to get this idea. Just slow, I guess.)

On-demand installation of packages

2 Answers2