Glossary

Overview

Learning a programming language is just like learning a spoken language: there are a lot of terms and definitions to learn! To complicate matters for an R / Python bilingualism context like this one, the two programming languages sometimes use the same term with very different definitions attached. To hopefully streamline term acquisition / comparison, I’m compiling a glossary of crucial R and Python terms below.

Note that if a definition has a term in both languages, the definition is given with the terms in the respective languages beneath. If a term is only found in one language it is given first and subsequently defined.

General Terms

• Data stored for later re-use (regardless of structure/dimensions)
  • Python – variable
  • R – object
• Category of information stored in a given data variable/object
  • Python – type
  • R – class
• Downloadable set of functions
  • Python & R – library / package
  • See “Tools” for definition of ‘function’

Data Types/Classes

• Numbers that are not a fraction (i.e., are a whole number)
  • Python & R – integer
  • Python pandas library – int64
• Non-integer numbers
  • Python – float
  • Python pandas library – float64
  • R – numeric
• Text / content stored as text
  • Python – string
  • Python pandas library – object
  • R – character
• Categorical content with an order among the unique entries (often–though not necessarily–with few unique entries relative to total number of entries)
  • R ONLY – factor
• Logical values indicating whether conditions are met
  • Python – boolean (True / False)
  • R – boolean (TRUE / FALSE / T / F)
• Variable/Object holding an ordered sequence of data (can be modified)
  • Python – list
  • R – vector (must be one-dimensional) / list
• Each component of a list/list
  • Python – item
  • R – element
• Variable holding an ordered sequence of data (cannot be modified)
  • Python ONLY – tuple [too-pull]

Operators

• Assignment operator – creates a new variable/object
  • Python – =
  • R – <- / ->
• Arithmetic operators – performs basic arithmetic
  • Python & R – addition (+)
  • Python & R – subtraction (-)
  • Python & R – multiplication (*)
  • Python & R – division (/)
  • Python – exponent (**)
  • R – exponent (^)
• Arithmetic assignment operator – does an arithmetic operation and stores the result in a variable
  • Python ONLY – arithmetic operator and assignment operator (e.g., +=)
• Relational operators – conditional statements that return boolean values
  • Python & R – ‘exactly equal to’ (==)
  • Python & R – ‘not equal to’ (!=)
  • Python & R – greater/less than (> / < respectively)
  • Python & R – greater/less than or equal to (>= / <= respectively)
• Namespacing operator – specifies library in which a given function is defined
  • Python – a period package.function (required)
  • R – two colons package::function (optional)

Tools

• variable/object containing multiple, inter-related operations that are run in a pre-defined order every time the variable/object is used
  • Python & R – function
• Value sent to a function when called to modify behavior (sometimes optional)
  • Python & R – argument / parameter
• Function that can only be used on a specific type/class of variable/object that supports arguments (sometimes optional) to modify behavior
  • Python – method (variable.method(...))
  • R – just a special case of function
• Function that can only be used on a specific type/class of variable/object without arguments to modify behavior
  • Python – attribute (variable.attribute)
  • R – just a special case of function

Data Characteristics

• Number of items/elements in a variable/object
  • Python – length (len())
  • R – length (length())
• Number of rows/columns in a two-dimension, tabular variable/object
  • Python – shape (.shape)
  • R – dimensions (dim())
• Number of characters in a string
  • Python – also length (len())
  • R – number of characters (nchar())