C++ Neural Networks and Fuzzy Logic: Preface

Figure 5.3

  The sigmoid function.

The Step Function

The step function is also frequently used as a threshold function. The function is 0 to start with and remains

so to the left of some threshold value ¸. A jump to 1 occurs for the value of the function to the right of ¸, and

the function then remains at the level 1. In general, a step function can have a finite number of points at which

jumps of equal or unequal size occur. When the jumps are equal and at many points, the graph will resemble a

staircase. We are interested in a step function that goes from 0 to 1 in one step, as soon as the argument

exceeds the threshold value ¸. You could also have two values other than 0 and 1 in defining the range of

values of such a step function. A graph of the step function follows in Figure 5.4.