ocvate常用函数

1.生成矩阵相关

https://www.coursera.org/learn/machine-learning/lecture/9fHfl/basic-operations

1. 初始化矩阵

a = [1,2; 3,4; 5,6]

a =

   1   2
   3   4
   5   6

v = 1: 6
v =

   1   2   3   4   5   6

v = 1: 1: 10
v =

    1    2    3    4    5    6    7    8    9   10

ones全1矩阵、

zeros全0矩阵、

rand随机矩阵（0 - 1）、

eye单位矩阵

one = ones(3, 3)
one =

   1   1   1
   1   1   1
   1   1   1

zero = zeros(1, 3)
zero =

   0   0   0

rand = rand(1, 3)
rand =

   0.55265   0.42458   0.14323

eye = eye(3)eye =

Diagonal Matrix

   1   0   0
   0   1   0
   0   0   1

2.矩阵操作

A =

   1   2
   3   4
   5   6

1.取某个元素

A(2,2)
ans =  4

2.取某一行

A(2,:)
ans =

   3   4

3.取某几行

A([1,3],:)
ans =

   1   2
   5   6

4.取某列

A(:,2)
ans =

   2
   4
   6

5.取某几列

6.修改某行或某列

A(:,2) = [4;6;8]
A =

   1   4
   3   6
   5   8

7.追加某行或某列

A = [A,[6;8;10]]
A =

    1    4    6
    3    6    8
    5    8   10

B = [1;2;3]
B =

   1
   2
   3

>> C = [A B]
C =

    1    4    6    1
    3    6    8    2
    5    8   10    3

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

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

   4
   5
   6

>> [B;D]
ans =

   1
   2
   3
   4
   5
   6

8.转换为列向量

A(:)
ans =

    1
    3
    5
    4
    6
    8
    6
    8
   10

9.取size

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

   1   2
   3   4
   5   6

>> size(A)
ans =

   3   2
ans_1 = size(A, 1)
ans_1 =  3
>> ans_2 = size(A, 2)
ans_2 =  2

10.取长度，其实是最长维度的长度

V = [1,2,3,4]
V =

   1   2   3   4

>> length(V)
ans =  4

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

   1   2
   3   4
   5   6
>> length(A)
ans =  3

3.命令行操作

1.输出当前所在目录

pwd

2.打印包含的文件

ls

3.切换目录

cd '../xxx'

4.载入数据（当前目录）

data1 = load('xxx.txt')

5.保存数据（当前目录）

save ans.txt v
save 文件名 数据