Please, help me understand working of this sigmoid function

1. Ixy2 =ImVar(S,1); %variance of 3*3 neighbour
2. for k = 1:D
3. minDd = min(min(Ixy2(:,:,k)));
4. meanDd = mean(mean(Ixy2(:,:,k)));
5. alpha = meanDd;
6. kk = log(0.01)/(minDd-alpha);
7. u(:,:,k) = 1-1./(1+exp(kk*(Ixy2(:,:,k)-alpha))); %weight calculated with Sigmoid functionu,:,:,k
8. end

I'm confused that whats happening after line four

[Image Analyst]

They're just creating temporary variables alpha and kk because otherwise the equation in line 7 would be super confusing and hard to follow.

[Fatima Rashid]

Yes I understand that, i'm confused with purposes of functions.

Means, why log0.01 is being divided by min-mean and so on.