What does the matlab code in steps 2 and 3 mean?

1.Hphi=Heaviside(phi,epsilon);
2.M(:,:,1)=Hphi;
3.M(:,:,2)=1-Hphi;
4.N_class=size(M,3);

Answer 1

[Wayne King]

M is a 3-D matrix.

 M(:,:,1) = Hphi;

Means set the first "page" of the 3rd dimension equal to the output of Heaviside with inputs phi and epsilon, which here is Hphi.

 M(:,:,2) = 1-Hphi;

Means set the second "page" of the 3rd dimension equal to 1-Hphi.

In general, M(:,:,index) is the way of assigning all rows and all columns of the index-th page of a 3D matrix a given value.

For example:

 M = zeros(2,2,2);  % M is 2x2x2
 M(:,:,1) = 1;  
 M(:,:,2) = 2;

Now M(:,:,1) is a 2x2 matrix of ones and M(:,:,2) is a 2x2 matrix of 2s.

   N_class = size(M,3);

Is just returning the size of M in the 3rd dimension

    M = ones(2,2,4);
    size(M,3)

Are you trying to read the Matlab documentation?