A sigmoid function is a function whose graph is shaped like the letter S. It could be defined as a differentiable bijection from the real numbers to an open interval , with . "The" sigmoid function , a special case of the logistic function. Other sigmoid functions include arctan and erf. One application of sigmoid functions is neural networks in AI programming. File:Confidence Space NCAAFB.jpg This statistics-related article contains minimal information concerning its topic. You can help the Mathematics Wikia by adding to it.