Packages and Namespaces

Defensive R Programming

Dr. Colin Gillespie

Jumping Rivers

Your global environment

The default environment is the .GlobalEnv
Objects are stored in environments
To view the contents, use ls()
This environment quickly fills up
We can start to mixing up objects

n
# or did I want
N

Packages and environments

Packages use namespaces as spaces for names
- You can think of a namespace as a box that contains the package
A namespace helps keep things tidy
- Sort of like folders

Exported functions

library() gives you direct access to this package box
library("dplyr") gives you direct access to the exported functions in dplyr

## 238 exported functions
getNamespaceExports("dplyr")

Alternatively, we can use :: to directly access a function

## The filter function from dplyr
dplyr::filter

Great minds think alike

Sometimes package authors come with the same function name

## The filter() function
stats::filter()
dplyr::filter()

If I type filter() which version do I get?
It depends on the package load order!

Great minds think alike

search() to the rescue

search()

# [1] ".GlobalEnv"         "package:dplyr"      "package:stats"  
# <Other packages>

Be defensive

Namespace clashes are more than just a pain

They can lead to hard to diagnose bugs

The conflicted package tries to make your function choice explicit

library("conflicted")
library("dplyr")

filter

#Error: [conflicted] `filter` found in 2 packages.
#Either pick the one you want with `::` 
# * dplyr::filter
# * stats::filter
#Or declare a preference with `conflict_prefer()`
# * conflict_prefer("filter", "dplyr")
# * conflict_prefer("filter", "stats")

Time to wake up

Defensive R Programming