[Rd] Trying to understand the search path and namespaces

Hadley Wickham hadley at rice.edu
Tue Nov 16 00:26:47 CET 2010

Hi all,

I'm trying to understand how the search path and namespaces interact.
For example, take the devtools package which suggests the testthat
package.  Here's what the search path looks like after I load each of
those packages:

> library(devtools)
> search()
 [1] ".GlobalEnv"        "package:devtools"  "package:stats"
 [4] "package:graphics"  "package:grDevices" "package:utils"
 [7] "package:datasets"  "package:methods"   "Autoloads"
[10] "package:base"
> library(testthat)
> search()
 [1] ".GlobalEnv"        "package:testthat"  "package:devtools"
 [4] "package:stats"     "package:graphics"  "package:grDevices"
 [7] "package:utils"     "package:datasets"  "package:methods"
[10] "Autoloads"         "package:base"

My question is this: when I execute the test function in devtools
function it calls the the test_package function in the testthat
package - but that function is located higher up the search path - how
does R find it?

(I ask this question because I'm trying to simulate package loading
from within R to simplify the development cycle, but something is
missing in my knowledge of namespaces, and so I have the devel
versions of my packages can't access packages that are loaded after
they are)


Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University

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