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copied!<p>You were close. Note what <code>?detach</code> has to say about the first argument <code>name</code> of <code>detach()</code>:</p> <blockquote> <p>Arguments:</p> <pre><code>name: The object to detach. Defaults to ‘search()[pos]’. This can be an unquoted name or a character string but _not_ a character vector. If a number is supplied this is taken as ‘pos’. </code></pre> </blockquote> <p>So we need to repeatedly call <code>detach()</code> once per element of <code>pkg</code>. There are a couple of other arguments we need to specify to get this to work. The first is <code>character.only = TRUE</code>, which allows the function to assume that <code>name</code> is a character string - it won't work without it. Second, we also probably want to unload any associated namespace. This can be achieved by setting <code>unload = TRUE</code>. So the solution is, for example:</p> <pre><code>pkg <- c("package:vegan","package:permute") lapply(pkg, detach, character.only = TRUE, unload = TRUE) </code></pre> <p>Here is a full example:</p> <pre><code>> require(vegan) Loading required package: vegan Loading required package: permute This is vegan 2.0-0 > sessionInfo() R version 2.13.1 Patched (2011-09-13 r57007) Platform: x86_64-unknown-linux-gnu (64-bit) locale: [1] LC_CTYPE=en_GB.utf8 LC_NUMERIC=C [3] LC_TIME=en_GB.utf8 LC_COLLATE=en_GB.utf8 [5] LC_MONETARY=C LC_MESSAGES=en_GB.utf8 [7] LC_PAPER=en_GB.utf8 LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_GB.utf8 LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods [7] base other attached packages: [1] vegan_2.0-0 permute_0.7-0 loaded via a namespace (and not attached): [1] grid_2.13.1 lattice_0.19-33 tools_2.13.1 > pkg <- c("package:vegan","package:permute") > lapply(pkg, detach, character.only = TRUE, unload = TRUE) [[1]] NULL [[2]] NULL > sessionInfo() R version 2.13.1 Patched (2011-09-13 r57007) Platform: x86_64-unknown-linux-gnu (64-bit) locale: [1] LC_CTYPE=en_GB.utf8 LC_NUMERIC=C [3] LC_TIME=en_GB.utf8 LC_COLLATE=en_GB.utf8 [5] LC_MONETARY=C LC_MESSAGES=en_GB.utf8 [7] LC_PAPER=en_GB.utf8 LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_GB.utf8 LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods [7] base loaded via a namespace (and not attached): [1] grid_2.13.1 lattice_0.19-33 tools_2.13.1 </code></pre> <p>If you want to turn this into a function, study the code in <code>sessionInfo()</code> to see how it identifies what it labels as "other attached packages:". Combine that bit of code with the idea above in a single function and you are home and dry. I'll leave that bit up to you though.</p>

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