Set function

In mathematics, a set function is a function whose input is a set. The output is usually a number. Often the input is a set of real numbers, a set of points in Euclidean space, or a set of points in some measure space.

Examples

Examples of set functions include:

 d(A) = \lim_{n\to\infty} \frac{|A \cap \{1,\dots,n\}|}{n},
assigning densities to sufficiently well-behaved subsets A  {1, 2, 3, ...}, is a set function.

References

Further reading


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