numerate {comprehenr}

Auxiliary functions for working with lists

Description

• numerate returns list of lists. Each list consists of two elements: sequential number of element and element. Reverse operation - unumerate.

• mark returns list of lists. Each list consists of two elements: name of element and element. Reverse operation - unmark.

• zip_lists combines lists side-by-sidy. Reverse operation - unzip_list.

• unzip_list is similair to matrix transposition but for list of lists.

• lag_list converts argument to list of arguments with previous values: x -> list(x[i-1], x[i]).

Usage

numerate(x)

enumerate(x)

unnumerate(x, item = 2)

mark(x)

unmark(x, item = 2)

unzip_list(x)

zip_lists(...)

lag_list(x)

Arguments

x

list, vector or list of lists

item

numeric number of list in which stored values

...

lists which will be zipped

Value

list or list of lists

Examples

cities = c('Chicago', 'Detroit', 'Atlanta')
airports = c('ORD', 'DTW', 'ATL')
pairs = zip_lists(cities, airports)

str(pairs)
str(unzip_list(pairs))

str(numerate(cities))

named_list = c('Chicago' = 'ORD', 'Detroit' = 'DTW', 'Atlanta' = 'ATL')
str(mark(named_list))

set.seed(123)
rand_sequence = runif(20)
# gives only locally increasing values
to_vec(for(`i, j` in lag_list(rand_sequence)) if(j>i) j)