Finite Temperature Variation - Heat Transfer

I am having trouble generating a coefficient matrix of different node types. Please take a look at my code and tell me where was my mistakes. My geometry cuts off at the top. Meaning it is half a node along the top.

%Under slant RIGHT SIDE
 for i= (.6*n^2)+1:(n*n)

     if (mod(i,n)==1+s);
             A(i,i-1)=1;
             A(i,i+1)=1;
             A(i,i)=((h*sqrt(2))/k)-2;
             g(i)=((h*sqrt(2))/k)*Tinf;

    %BOTTOMROW!!!
    %  Last line    
       elseif (mod(i,n)==0)
          A(i,i-1)= 1;           
        A(i,i)=-3;
          A(i,i-n)=1;
          A(i,i+n)=1;
          g(i)=0;  
      s=s+1;

              %last column
  elseif (i==((n*n)-.4*n)+1)
          A(i,i-1)= 1;           
        A(i,i)=-3;
          A(i,i-n)=1;
          A(i,i+n)=1;
          g(i)=0;
   %bottom right corner(n^2)
   elseif (i==n*n)
        A(i,i-1)= 1;           
        A(i,i)=-2;
          A(i,i-n)=1;
          g(i)=0;

     %Right side under slant %non-gen in between gen and slant 
       else
           A(i,i+1)=1;
           A(i,i-n)=1;
           A(i,i+n)=1;
           A(i,i-1)=1;
           A(i,i)=-4;
           g(i)=0;

       end
   end 

T=A\g';
T( ~any(T,2), : ) = [];  %rows

a = T == 10; 
T(a) = NaN;

T2= abs(real(T));

Temp = vec2mat(T2,n);

Temp1=diag(((.6*n^2)+1),0);
surf(Temp)