Vectors and Matrices

Array Creation Functions

创建随机数矩阵

x = rand(2)
x = 
    0.8147    0.1270
    0.9058    0.9134
    
x = rand(2,3)
x = 
    0.6324    0.2785    0.9575
    0.0975    0.5469    0.9649

获得已知矩阵的大小

size(x)

Indexing into and Modifying Arrays

Indexing into Arrays (Indexing into Arrays)

%You can extract values from an array using *row, column indexing*.
y = A(5,7)

%This syntax extracts the value in the 5th row and 7th column of `A` 
%and assigns the result to the variable `y`.

If you only use one index with a matrix, it will traverse down each column in order.

按列分配

%When used as an index, the colon operator (`:`) specifies all the elements in that dimension. The syntax
% 行
x = A(2,:)
% 列
y = A(:,2)

%creates a row vector containing all of the elements from the second row of `A`.
x = A(1:3,:)%三行
volumes=data(:,3:4)%3 4列