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function res = sigmoidzhang(x)
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%Another option - SID-sigmoid...
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%Ref:Efficient digital implementation of the sigmoid
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%function for reprogrammable logic
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%M.T. Tommiska
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%referenced from Zhang, Vassiliadis and Delgago's paper
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x = min(x,4);
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x = max(x,-4);
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sgn = sign(x);
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x = x.*sgn;
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y = (1/2) .* ((1.-abs(0.25.*x)).^2);
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res = y;
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res(sgn>0) = 1-res(sgn>0);
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end
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