Sigmoid Function(S形函数) This function can range 1-9 between o and l. but it is also sometimes useful to use the -1 to I range. An 21+ example of the sigmoid function is the hyperbolic tangent function(双曲正切函数) This function can range between 0 and 1, but it is also sometimes useful to use the -1 to 1 range. An example of the sigmoid function is the hyperbolic tangent function(双曲正切函数)