R Data Structures and Algorithms

Dictionaries

A dictionary can be defined as an ordered or unordered list of key-element pairs, where keys (usually unique) are used to locate elements (not necessary unique) in the data structure. For example, a data structure that stores customer information in a retail shop can be considered as a dictionary, where the consumer ID serves as the key for identification of different customers. Dictionaries are also known as associative arrays or maps, as they map keys to values to perform retrieval operations such as addition, removal, and search. Every element of a dictionary consists of a key and an associated element, also known as a key-value pair. This is shown in Figure 4.11:

Figure 4.11: Dictionary key-value pair structure

The key in a dictionary ...