【机器学习】Octave矩阵，向量的表示

CS229中需要用到Octave来做，张量的存储是必备的知识点，记录一下备用：

% The ; denotes we are going back to a new row.
A = [1, 2, 3; 4, 5, 6; 7, 8, 9; 10, 11, 12]

% Initialize a vector 
v = [1;2;3] 

% Get the dimension of the matrix A where m = rows and n = columns
[m,n] = size(A)

% You could also store it this way
dim_A = size(A)

% Get the dimension of the vector v 
dim_v = size(v)

% Now let's index into the 2nd row 3rd column of matrix A
A_23 = A(2,3)

矩阵加减乘除法

% Initialize matrix A and B 
A = [1, 2, 4; 5, 3, 2]
B = [1, 3, 4; 1, 1, 1]

% Initialize constant s 
s = 2

% See how element-wise addition works
add_AB = A + B 

% See how element-wise subtraction works
sub_AB = A - B

% See how scalar multiplication works
mult_As = A * s

% Divide A by s
div_As = A / s

% What happens if we have a Matrix + scalar?
add_As = A + s

举个例子

【机器学习】Octave矩阵，向量的表示

代码：

house_sizes = [1,2104; 1,1416; 1,1534; 1, 852]
W = [-40; 0.25]
res = house_sizes * W
% 输出
res =

   486.00
   314.00
   343.50
   173.00

END.