A = [1 1 1; -1 1 -1; 2 1 -1; -1 1 0];
b = [3 1 1 4]'; p = [1 -2 -1];

T = totbl(-A,-b,p);
              x1         x2         x3         1   
       --------------------------------------------
 x4 = |    -1.0000    -1.0000    -1.0000     3.0000 
 x5 = |     1.0000    -1.0000     1.0000     1.0000 
 x6 = |    -2.0000    -1.0000     1.0000     1.0000 
 x7 = |     1.0000    -1.0000    -0.0000     4.0000 
       --------------------------------------------
 z  = |     1.0000    -2.0000    -1.0000     0.0000 

T = ljx(T,2,2);
              x1         x5         x3         1   
       --------------------------------------------
 x4 = |    -2.0000     1.0000    -2.0000     2.0000 
 x2 = |     1.0000    -1.0000     1.0000     1.0000 
 x6 = |    -3.0000     1.0000     0.0000     0.0000 
 x7 = |     0.0000     1.0000    -1.0000     3.0000 
       --------------------------------------------
 z  = |    -1.0000     2.0000    -3.0000    -2.0000 

T = ljx(T,1,3);
              x1         x5         x4         1   
       --------------------------------------------
 x3 = |    -1.0000     0.5000    -0.5000     1.0000 
 x2 = |     0.0000    -0.5000    -0.5000     2.0000 
 x6 = |    -3.0000     1.0000    -0.0000     0.0000 
 x7 = |     1.0000     0.5000     0.5000     2.0000 
       --------------------------------------------
 z  = |     2.0000     0.5000     1.5000    -5.0000 


A = [1 1 1 1 0 0 0; -1 1 -1 0 1 0 0; 2 1 -1 0 0 1 0; -1 1 0 0 0 0 1];
b = [3 1 1 4]'; p = [1 -2 -1 0 0 0 0]';
B = [4 5 6 7]; N = [1 2 3];
[L,U] = lu(A(:,B));
h = U\(L\b)

h =

     3
     1
     1
     4

u = L'\(U'\p(B));
c = p(N)' - u'*A(:,N)

c =

     1    -2    -1

s = 2;
d = U\(L\A(:,N(s)))

d =

     1
     1
     1
     1

r = 2;
swap = B(r); B(r) = N(s); N(s) = swap;
[L,U] = lu(A(:,B));
h = U\(L\b)

h =

     2
     1
     0
     3

u = L'\(U'\p(B));
c = p(N)' - u'*A(:,N)

c =

    -1     2    -3

s = 3;
d = U\(L\A(:,N(s)))

d =

     2
    -1
     0
     1

r = 1;
swap = B(r); B(r) = N(s); N(s) = swap;
[L,U] = lu(A(:,B));
h = U\(L\b)

h =

     1
     2
     0
     2

u = L'\(U'\p(B));
c = p(N)' - u'*A(:,N)

c =

    2.0000    0.5000    1.5000