Neurocomputing in Complex Domain - High Dimensional Neurocomputing: Growth, Appraisal and Applications - page 52

Fig. 3.2 a Real part of Haykin activation (sigmoid function). b Imaginary part of Haykin activation.
c Real part of the derivative with respect to x. d Imaginary part of the derivative with respect to x.
e Real part of the derivative with respect to y. f Imaginary part of the derivative with respect to y