Persist Attributes Across Data Operations.
Sticky: Persistent Attributes
In base R, objects lose attributes in many common operations such as: subset, [, [[<-, append, etc. or when inserted into or extracted from recursive (list-like) objects such as data frames or data tables. Marking objects 'sticky', make attributes resilient to these operations. In essence, sticky makes object behave more like objects in other languages whose attributes are preserved. There isn't much to the package. sticky
/unstick
and sticky_all
are the only interfaces to the package.
Key Functions
sticky
: make an objects attributes persist across data operationsunstick
: remove the stickiness of an object; attributes will no longer persist during common data operationssticky_all
: make all elements of a recursive object (e.g list, data frames, etc.) sticky.
Example
Here is an simple example of a sticky attribute in action. Under base R, attributes do not survive a slice/subset/[
operation:
x <- 1:5
attr(x, 'foo') <- 'bar'
attr(x[1:3],'foo') # NULL -- attribute removed
To ensure that they get preserved, simply declare the object as sticky
:
x <- sticky(x)
attr(x[1:3],'foo') # 'bar' -- attribute preserved
sticky()
works for vectors inside table-like objects ( i.e. data.frames and data.tables), preserving their attributes during table operations.
df <- data.frame(
sticky = sticky( structure(1:5, foo="bar") ),
nonstick = structure( letters[1:5], foo="baz" )
)
attr( df[2:3,"nonstick"], 'foo' ) # NULL
attr( df[2:3,"sticky"], 'foo' ) # bar
If all elements of a list or a data.frame need to behave in a sticky manner, use sticky_all
.
df <- sticky_all(df)
attr( df[2:3,"nonstick"], 'foo' ) # Now 'baz'
Installation
Stable Version: CRAN (coming soon)
install.packages('sticky')
Development Version: Github
library(devtools)
lnstall_github('decisionpatterns/sticky')
Use Cases
There are a number of things that can be done with sticky
:
- Preserve attributes of atomic or recursive objects
- Ensure that attributes of vectors in data.[frame|table] are preserved
- Build a basic class system.
References
The issue of attribute resilience has been often asked and debated. Here are a few of the most prevalent discussions.