rlist is a set of tools for working with list objects. Its goal is to make it easier to work with lists by providing a wide range of functions on non-tabular data stored in them.
This package supports list filtering, mapping, grouping, sorting, updating, searching, file input/output, and many other functions. It implements collection pipeline and strongly recommends functional programming style in list operations.
- API Break:
list.searchnow evaluates expression recursively in a list and supports limited lambda expression (only value is defined). - Add
equal()function for logical and fuzzy filtering and searching which supports exact equality, atomic equality, inclusion, pattern matching, string-distance tolerance. - Add
List()to provide an environment in which most list functions are defined for light-weight chaining that does not reply on external operators.
You can install the latest released version from CRAN with
install.packages("rlist")or the latest development version from GitHub with
devtools::install_github("rlist","renkun-ken")The package provides a wide range of high-level functions to work with list objects.
Suppose we have a list of developers, each of whom has a name, age, a few interests, a list of programming languages they use and the number of years they have been using them.
library(rlist)
devs <-
list(
p1=list(name="Ken",age=24,
interest=c("reading","music","movies"),
lang=list(r=2,csharp=4,python=3)),
p2=list(name="James",age=25,
interest=c("sports","music"),
lang=list(r=3,java=2,cpp=5)),
p3=list(name="Penny",age=24,
interest=c("movies","reading"),
lang=list(r=1,cpp=4,python=2)))This type of data is non-relational since it does not well fit the shape of a data table yet it can be easily stored in JSON or YAML format. In R, list object is powerful enough to represent a wide range of non-relational datasets like this. This package provides a wide range of functions to query this type of data.
Filter those who like music and has been using R for more than 3 years.
subset1 <- list.filter(devs, "music" %in% interest & lang$r >= 3)
str(subset1)List of 1
$ p2:List of 4
..$ name : chr "James"
..$ age : num 25
..$ interest: chr [1:2] "sports" "music"
..$ lang :List of 3
.. ..$ r : num 3
.. ..$ java: num 2
.. ..$ cpp : num 5
Select their names and ages.
subset2 <- list.select(devs, name, age)
str(subset2)List of 3
$ p1:List of 2
..$ name: chr "Ken"
..$ age : num 24
$ p2:List of 2
..$ name: chr "James"
..$ age : num 25
$ p3:List of 2
..$ name: chr "Penny"
..$ age : num 24
Map each of them to the number of interests.
result <- list.map(devs, length(interest))
str(result)List of 3
$ p1: int 3
$ p2: int 2
$ p3: int 2
In this package, almost all functions that work with expressions accept the following forms of lambda expressions:
- Implicit lambda expression:
g(x) - Univariate lambda expressions:
x ~ g(x)x -> g(x)f(x) -> g(x)
- Multivariate lambda expressions:
f(x,i) -> g(x,i)f(x,i,name) -> g(x,i,name)
where x refers to the list member itself, i denotes the index, name denotes the name. If the symbols are not explicitly declared, ., .i and .name will by default be used to represent them, respectively.
nums <- list(a=c(1,2,3),b=c(2,3,4),c=c(3,4,5))
list.map(nums, c(min=min(.),max=max(.)))
list.filter(nums, x -> mean(x)>=3)
list.map(nums, f(x,i) -> sum(x,i))Query the name of each developer who likes music and uses R, and put the results in a data frame.
library(pipeR)
devs %>>%
list.filter("music" %in% interest & "r" %in% names(lang)) %>>%
list.select(name,age) %>>%
list.stack name age
1 Ken 24
2 James 25
The example above uses pipeR(http://renkun.me/pipeR/) package for pipeline operator %>>% that chains commands in a fluent style.
List() function wraps a list within an environment where almost all list functions are defined. Here is the List-environment version of the previous example.
m <- List(devs)
m$filter("music" %in% interest & "r" %in% names(lang))$
select(name,age)$
stack()$
data name age
1 Ken 24
2 James 25
The package also provides detailed vignettes for most functions.
- Introduction to rlist
- List Mapping
- List Filtering
- List Sorting
- List Grouping
- List Joining
- List Updating
- List Searching
- List Input/Output
- Lambda expressions
- List environment
- Examples
help(package = rlist)or view the documentation on CRAN
This package is under MIT License.