第二周 第三部分

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

   1   2
   3   4
   5   6

>> A(3,2)
ans =  6

>> A(2,:) %该行或列的所有元素
ans =

   3   4


>> A(:,2)
ans =

   2
   4
   6
>> A([1 3], :) %取第一、三行的元素 
ans =

   1   2
   5   6

>> A(:,2) = [0; 0; 0] %赋值给A的第二列
A =

   1   0
   3   0
   5   0
>> A = [A,[10;11;12]];%再加一列
>> A
A =

    1    0   10
    3    0   11
    5    0   12
>> A(:)%把A所有的元素一向量形式表示
ans =

    1
    3
    5
    0
    0
    0
   10
   11
   12

>> A
A =

    1    0   10
    3    0   11
    5    0   12

>> B = [36 12;23 0; 56 12]
B =

   36   12
   23    0
   56   12

>> C  =[A B]
C =

    1    0   10   36   12
    3    0   11   23    0
    5    0   12   56   12



>> C = [A;B]%AB行数一样就可以
error: vertical dimensions mismatch (3x3 vs 3x2)
>> A = [1 0;3 0;5 0]
A =

   1   0
   3   0
   5   0

>> C = [A;B]
C =

    1    0
    3    0
    5    0
   36   12
   23    0
   56   12

>> A =[1;2;3]
A =

   1
   2
   3

>> C = [A;B]
error: vertical dimensions mismatch (3x1 vs 3x2)
>>

%这2种方式一样的
>> [A,B]
ans =

    1   36   12
    2   23    0
    3   56   12

>> [AB]
error: 'AB' undefined near line 1 column 2
>> [A B]
ans =

    1   36   12
    2   23    0
    3   56   12