An alternative module system for R
This package provides an alternative mechanism of organising reusable code into units, called “modules”. Its usage and organisation is reminiscent of Python’s. It is designed so that normal R source files are automatically modules, and need not be augmented by meta information or wrapped in order to be distributed, in contrast to R packages.
Modules are loaded via the syntax
module = import('module')
moduleis the name of a module. Like in Python, modules can be grouped together in submodules, so that a name of a module could be, e.g.
tools/strings. This could be used via
str = import('tools/strings')
This will import the code from a file with the name
tools/strings.r, located either under the local directory or at a predefined, configurable location.
Exported functions of the module could then be accessed via
some_string = 'Hello, World!' upper = str$to_upper(some_string) # => 'HELLO, WORLD!'
Notice that we’ve aliased the actual module name to
strin user code.
Alternatively, modules can be imported into the global namespace:
import('tools/strings', attach = TRUE)
The module is then added to R’s
search()vector (or equivalent) so that functions can be accessed without qualifying the module’s imported name each time.
R modules are normal R source files. However,
importis different from
sourcein some crucial regards. It’s also crucially different from normal packages. Please refer to the comparison for details.
Not to worry, simply use
importand treat the imported package the same way you would treat a module:
dplyr = import_package('dplyr') cars %>% dplyr$filter(speed > 15)
requireshould not be used in conjunction with modules (although they can).
To install using devtools, just type the following command in R:
Wiki: Installation has more information.
Local, single-file modules can be used as-is: assuming you have a file called
foo.rin your current directory, execute
foo = import('foo') # or: foo = import('./foo')
in R to make its content accessible via a module, and use it via
foo$function_name(…). Alternatively, you can use
import('foo', attach = TRUE)
But this form is usually discouraged (at the file scope) since it clutters the global search path (although it’s worth noting that modules are isolated namespaced and don’t leak their scope).
If you want to access a module in a non-local path, the cleanest way is to create a central repository (e.g. at
~/.R/modules) and to copy module source files there. Now
importneeds to know how to find this repository. This can be done by either setting the environment variable
R_IMPORT_PATHor, inside R (e.g. in
Nested modules (called “packages” in Python, but for obvious reasons this name is not used for R modules) are directories (either local, or in the import search path) which optionally contain an
__init__.rfile. Assuming you have such a module
foo, inside which is a submodule
bar, you can then make it available in R via
foo = import('foo') # Make available foo, or bar = import('foo/bar') # Make available only foo/bar
During module development, you can
reloada module to reflect its changes inside R, or
unloadit. In order to do this, you need to have assigned the result of
importto an identifier.