kv - key-value-index iteration in R

Other languages (e.g. Python) have a native,shorthand way to reference an object's key or values while iterating. R does not. This is where kv steps in.

Key/Value/Index Iteration

kv provides a simple/no magic mechanism for key-value-index iteration. It is best illustrated by the simple example:

mylist = list( a=1, b=2, c=3)              # List to iterate over

for( . in kv(mylist) )
  cat( "key is: ", .$k, "| value is:", .$v, "\n" )
}  

kv works by transforming its argument into a list-of-lists, each element having the appropriate k and v. See ?kv for details.

NB: the use of . is a convention, any valid R name will work in its place.

There are also additional funtions:

• kvi(): uses keys, values and indexes
• kv() : uses keys and values
• ki() : uses keys and indexes
• vi() ; uses values and indexes

Table-row iterations

kv also allows for iteration over rows in a table, for example:

for( . in each_row(iris) )
  cat( .$Species, ": ", .$Sepal.Lenght )

Installation

Latest Release:

install.packages('kv')  # Soon

Development Version:

install.packages('devtools')
devtools::install_github('decisionpatterns/kv')

Functions

The function of this packages are permutation of letters 'k', 'v' and 'i'. Each function turns its argument into a list-of-lists with the corresponding (k)ey, (v)alue and/or (i) set.

The use of . is a simple convention that allows use to use the concise syntak .$k, .$v or .$i to access the element.

References

• SO:for-loop-in-r-with-key-value
• SO:iterate-over-key-value-pair-from-a-list