23-Oct-2013


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

   1  -2
   5   4
  -3   0



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

  -3   5   0   1
   2  -7   4  -1



3> C = A * B
C =

   -7   19   -8    3
   -7   -3   16    1
    9  -15    0   -3



4> B * A
error: operator *: nonconformant arguments (op1 is 2x4, op2 is 3x2)


4> a = [1 0; 0 0]
a =

   1   0
   0   0



5> b = [0 1; 0 1]
b =

   0   1
   0   1



6> a * b
ans =

   0   1
   0   0



7> b * a
ans =

   0   0
   0   0



8> % divisori dello zero


8> zeros(2,2)
ans =

   0   0
   0   0



9> zeros(4,1)
ans =

   0
   0
   0
   0



10> % scambiare righe e colonne (e colonne e righe); trasposta


10> A
A =

   1  -2
   5   4
  -3   0



11> A'  % matrrice trasposta di A
ans =

   1   5  -3
  -2   4   0



12> zero = zeros(4,1)
zero =

   0
   0
   0
   0



13> zero'
ans =

   0   0   0   0



14> v = [1+3i, -3+4i]
v =

   1 + 3i  -3 + 4i



15> v'  % trasposta coniugata
ans =

   1 - 3i
  -3 - 4i



16> v.'  % trasposta (senza passare al complesso coniugato)
ans =

   1 + 3i
  -3 + 4i



17> A
A =

   1  -2
   5   4
  -3   0



18> A^2
error: for A^b, A must be a square matrix


18> A.^2
ans =

    1    4
   25   16
    9    0



19> 


19> A + B
error: operator +: nonconformant arguments (op1 is 3x2, op2 is 2x4)


19> E = [1 -7; 5 -8; -5 1]
E =

   1  -7
   5  -8
  -5   1



20> size(A)
ans =

   3   2



21> size(E)
ans =

   3   2



22> size(size(E))
ans =

   1   2



23> A + E
ans =

    2   -9
   10   -4
   -8    1



24> A - E
ans =

    0    5
    0   12
    2   -1



25> 3*A
ans =

    3   -6
   15   12
   -9    0



26> 3*A - 5*E
ans =

   -2   29
  -10   52
   16   -5



27> % definire funzioni


27> f = inline('x.^2', 'x')
f = f(x) = x.^2


28> x
error: 'x' undefined near line 28 column 1


28> 'x'
ans = x


29> f(-4)
ans =  16


30> f([-2 -1 0 1 2])
ans =

   4   1   0   1   4



31> f([-2 -1 ; 1 2])
ans =

   4   1
   1   4



32> g = inline('a*x.^2', 'a', 'x')
g = f(a, x) = a*x.^2


33> g(5,3)
ans =  45


34> % anonymous function; function handle @


34> h = @(x) 1./x
h =

@(x) 1 ./ x



35> h(4)
ans =  0.25000


36> edit nostra_funzione.m


37> pwd
ans = C:\cygwin\home\achilles


38> help nostra_funzione
'nostra_funzione' is a function from the file C:\cygwin\home\achilles\nostra_funzione.m

 nostra_funzione(x) calcola sin x / x

Additional help for built-in functions and operators is
available in the online version of the manual.  Use the command
'doc <topic>' to search the manual index.

Help and information about Octave is also available on the WWW
at http://www.octave.org and via the help@octave.org
mailing list.


39> x = linspace(-2*pi,2*pi);


40> plot(x, nostra_funzione(x));


41> quit