In mathematics, by sigma function one can mean one of the following:
* The
sum-of-divisors function σ
''a''(''n''), an arithmetic function
*
Weierstrass sigma function, related to elliptic functions
* Rado's sigma function, see
busy beaver
See also
sigmoid function
A sigmoid function is a mathematical function having a characteristic "S"-shaped curve or sigmoid curve.
A common example of a sigmoid function is the logistic function shown in the first figure and defined by the formula:
:S(x) = \frac = \ ...
.
{{mathdab