28-Oct-2013


1> eye(2)
ans =

Diagonal Matrix

   1   0
   0   1



2> eye(2,2)
ans =

Diagonal Matrix

   1   0
   0   1



3> diag([1 1])
ans =

Diagonal Matrix

   1   0
   0   1



4> diag([1 2 3 4 5])
ans =

Diagonal Matrix

   1   0   0   0   0
   0   2   0   0   0
   0   0   3   0   0
   0   0   0   4   0
   0   0   0   0   5



5> diag(ans)
ans =

   1
   2
   3
   4
   5



6> A = [1 -5 4; 0 7 -2; 3 -3 1]
A =

   1  -5   4
   0   7  -2
   3  -3   1



7> % matrice inversa


7> B = inv(A)
B =

  -0.018868   0.132075   0.339623
   0.113208   0.207547  -0.037736
   0.396226   0.226415  -0.132075



8> A * B
ans =

   1.00000   0.00000   0.00000
   0.00000   1.00000   0.00000
   0.00000  -0.00000   1.00000



9> B * A
ans =

   1.00000   0.00000   0.00000
   0.00000   1.00000  -0.00000
   0.00000  -0.00000   1.00000



10> C = [1 2 3; 4 5 6; 7 8 9]
C =

   1   2   3
   4   5   6
   7   8   9



11> inv(C)
ans =

  -4.5036e+015  9.0072e+015  -4.5036e+015
  9.0072e+015  -1.8014e+016  9.0072e+015
  -4.5036e+015  9.0072e+015  -4.5036e+015



12> SC = B * C
SC =

   2.88679   3.33962   3.79245
   0.67925   0.96226   1.24528
   0.37736   0.86792   1.35849



13> DC = C * B
DC =

   1.39623   1.22642  -0.13208
   2.86792   2.92453   0.37736
   4.33962   4.62264   0.88679



14> SC2 = A \ C
SC2 =

   2.88679   3.33962   3.79245
   0.67925   0.96226   1.24528
   0.37736   0.86792   1.35849



15> SC - SC2
ans =

  4.4409e-016  4.4409e-016  -4.4409e-016
  1.1102e-016  1.1102e-016  2.2204e-016
  -1.6653e-016  1.1102e-016  2.2204e-016



16> DC2 = C/A
DC2 =

   1.39623   1.22642  -0.13208
   2.86792   2.92453   0.37736
   4.33962   4.62264   0.88679



17> % risolvere un sistema lineare Ax = b


17> A = [2 -3; 1 5]
A =

   2  -3
   1   5



18> b = [1 ; 2]
b =

   1
   2



19> x = sol, soluzione:


19> sol = A \ b
sol =

   0.84615
   0.23077



20> A * sol 
ans =

   1
   2



21> % matrice casuale


21> A = rand(2,3)
A =

   0.524180   0.217144   0.917128
   0.073920   0.995202   0.960508



22> 1000 * rand(2,3)
ans =

   765.68   969.04   263.38
   914.98   558.61   133.34



23> 1000 * rand(2,3)
ans =

   766.972   279.616   660.945
    69.584   562.771   172.224



24> 1000 * rand(2,3)
ans =

   722.7849    12.7253   403.6388
    23.2961   286.8400     1.4785



25> quit