detach all packages while working in R

Question

While working to solve another problem I got this problem:

I can remove all R objects by:

rm(list = ls(all = TRUE))

Is there equivalent command that can detach installed packages during working session?

> sessionInfo()
R version 2.12.2 (2011-02-25)
Platform: i386-pc-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base 

require(ggplot2)

Loading required package: ggplot2
Loading required package: reshape
Loading required package: plyr

Attaching package: 'reshape'

The following object(s) are masked from 'package:plyr':

    round_any

Loading required package: grid
Loading required package: proto

sessionInfo()

R version 2.12.2 (2011-02-25)
Platform: i386-pc-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods  
[8] base     

other attached packages:
[1] ggplot2_0.8.9 proto_0.3-9.1 reshape_0.8.4 plyr_1.4 

I tried this way, although even it worked in not a global solution :

pkg <- c("package:ggplot2_0.8.9", "package:proto_0.3-9.1", "package:reshape_0.8.4",  "package:plyr_1.4")

 detach(pkg, character.only = TRUE)

Error in detach(pkg, character.only = TRUE) : invalid 'name' argument
In addition: Warning message:
In if (is.na(pos)) stop("invalid 'name' argument") :
  the condition has length > 1 and only the first element will be used

What I am loking for is something global like:

  rm(list = ls(all = TRUE))

for objects, expect it would not remove attached base packages

thanks;

Answer 1

So, someone should have simply answered the following.

lapply(paste('package:',names(sessionInfo()$otherPkgs),sep=""),detach,character.only=TRUE,unload=TRUE)

(edit: 6-28-19) In the latest version of R 3.6.0 please use instead.

invisible(lapply(paste0('package:', names(sessionInfo()$otherPkgs)), detach, character.only=TRUE, unload=TRUE))

Note the use of invisible(*) is not necessary but can be useful to prevent the NULL reply from vertically spamming the R window.

(edit: 9/20/2019) In version 3.6.1

It may be helpful to convert loaded only names(sessionInfo()$loadedOnly) to explicitly attached packages first, and then detach the packages, as so.

lapply(names(sessionInfo()$loadedOnly), require, character.only = TRUE)
invisible(lapply(paste0('package:', names(sessionInfo()$otherPkgs)), detach, character.only=TRUE, unload=TRUE, force=TRUE))

One can attempt to unload base packages via $basePkgs and also attempt using unloadNamespace(loadedNamespaces()). However these typically are fraught with errors and could break basic functionality such as causing sessionInfo() to return only errors. This typically occurs because of a lack of reversibility in the original package's design. Currently timeDate can break irreversibly, for example.

(edit: 9/24/20) for version 4.0.2 The following first loads packages to test and then gives a sequence to fully detach all packages except for package "base" and "utils". It is highly recommended that one does not detach those packages.

    invisible(suppressMessages(suppressWarnings(lapply(c("gsl","fBasics","stringr","stringi","Rmpfr"), require, character.only = TRUE))))
    invisible(suppressMessages(suppressWarnings(lapply(names(sessionInfo()$loadedOnly), require, character.only = TRUE))))
    sessionInfo()

    #the above is a test

    invisible(lapply(paste0('package:', c("stringr","fBasics")), detach, character.only=TRUE,unload=TRUE))
    #In the line above, I have inserted by hand what I know the package dependencies to be. A user must know this a priori or have their own automated
    #method to discover it. Without removing dependencies first, the user will have to cycle through loading namespaces and then detaching otherPkgs a
    #second time through.
    invisible(lapply(paste0('package:', names(sessionInfo()$otherPkgs)), detach, character.only=TRUE,unload=TRUE))

    bspkgs.nb<-sessionInfo()$basePkgs[sessionInfo()$basePkgs!="base"]
    bspkgs.nbu<-bspkgs.nb[bspkgs.nb!="utils"]
    names(bspkgs.nbu)<-bspkgs.nbu
    suppressMessages(invisible(lapply(paste0('package:', names(bspkgs.nbu)), detach, character.only=TRUE,unload=TRUE)))

    #again this thoroughly removes all packages and loaded namespaces except for base packages "base" and "utils" (which is highly not recommended).