Page "Mathematical analysis" Paragraph 42

As the above section on topological spaces makes clear, analysis isn't just about continuity in the traditional sense of real numbers.

Analysis is fundamentally about functions, the spaces that the functions act on and the function spaces that the functions themselves are members of.

A discrete function f ( n ) is usually called a sequence a ( n ).

A sequence could be a finite sequence from some data source or an infinite sequence from a discrete dynamical system.

A discrete function could be defined explicitly by a list, or by a formula for f ( n ) or it could be given implicitly by a recurrence relation or difference equation.

A difference equation is the discrete equivalent of a differential equation and can be used to approximate the latter or studied in its own right.

Every question and method about differential equations has a discrete equivalent for difference equations.

For instance where there are integral transforms in harmonic analysis for studying continuous functions or analog signals, there are discrete transforms for discrete functions or digital signals.

As well as the discrete metric there are more general discrete or finite metric spaces and finite topological spaces.