What is the benefit of import in a namespace in R? -

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R's namespace mechanism assigns a export function which is then visible to the user. In addition, it allows the import functions from other packages, while the profit of exports is clear, I have more problems in understanding the benefits of import.

An advantage seems to be that any one can use the function from other packages without enclosing the package and thereby saving the memory is an example in this section.

However, the import function should have other benefits. Specifically, the namespace of stats4 package shows: 

  importFrom ("graphics", plot) importFrom ("stats", optim, qchisq) # # For these, we define methods or (AIC, BIC, Novus) a general generic: importFrom ("statistics", AIC, BIC, COF, clerk, loglink, nodes, profiles, updates, vcov) Export Classes ( Mail, profile., Summary.mL) # # All methods for imported generic: export methods (COEF, CONFY ## Indirect generics who have no way to export here (AIC, BIC, Knox) ​​are imported here   
 There are functions which are neither S4 Class nor Generic (where it will also be understood to use the import, as mentioned in the example), but   
 
  
  
  
  
 / code>,  optim  or  qchisq  code?  
  
 
 
 If the function  foo  is imported from the package bar, then found it What does the user do for his search path, for example, by appending a package falcon, in which the function is  foo  without a namespace, package code suddenly  Baz :: Using foo . There are also issues of efficiency (instead of searching through all the symbols on the search path, are found instantly), but it is likely to be trivial for most applications. In the same way, due to the least collision (or the use of unexpected works) and more efficient lookup,  importFrom  is a code  import .  
 Things can be quite complex with S4 (and S3). A non-generic function such as  graphics :: plot  can be promoted in two different packages with a normal (with  setGeneric ), and each generic has its own There may be a set of methods. A package author wants to be precise, about which  plot  is normal, and so see the methods of dispatch tables, their classes and methods.  
  pkg :: Foo  always resolves the desired function, it is necessary that PKG was listed in the despectors: field of DESCRIPTION file (maybe in import : But then it seems like a misleading advertisement to not import from PKG), pollutes the user's search path, it includes two symbol lookup and function calls ( :: ); And these are less efficient. The carefully-extended part of the laziness and lack of sight also sees the use of tedious and error prone as  :: .  
 The package (user name and password via the svn  readonly ) can generate a NAMESPACE file from an existing package (or at least this is a recent change in the R- Before NAMESPACE started without any package; I have not tried codetoolsBioC on such a package).

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