# MATLAB冒号符号

冒号（:)是最有用的运算符在MATLAB之一。它是用来创建矢量，下标数组和指定的迭代。

`1:10`

MATLAB执行该语句，并返回一个行向量，包含从1到10的整数：

```ans =
1     2     3     4     5     6     7     8     9    10
```

`100: -5: 50`

MATLAB执行该语句，并返回以下结果：

```ans =
100    95    90    85    80    75    70    65    60    55    50
```

`0:pi/8:pi`

MATLAB执行该语句，并返回以下结果：

```ans =
Columns 1 through 7
0    0.3927    0.7854    1.1781    1.5708    1.9635    2.3562
Columns 8 through 9
2.7489    3.1416
```

A(:,j) is the jth column of A.
A(i,:) is the ith row of A.
A(:,:) is the equivalent two-dimensional array. For matrices this is the same as A.
A(j:k) is A(j), A(j+1),...,A(k).
A(:,j:k) is A(:,j), A(:,j+1),...,A(:,k).
A(:,:,k) is the kth page of three-dimensional array A.
A(i,j,k,:) is a vector in four-dimensional array A. The vector includes A(i,j,k,1), A(i,j,k,2), A(i,j,k,3), and so on.
A(:) is all the elements of A, regarded as a single column. On the left side of an assignment statement, A(:) fills A, preserving its shape from before. In this case, the right side must contain the same number of elements as A.

## 例子

```A = [1 2 3 4; 4 5 6 7; 7 8 9 10] A(:,2) % second column of A
A(:,2:3) % second and third column of A
A(2:3,2:3) % second and third rows and second and third columns```

```A =
1     2     3     4
4     5     6     7
7     8     9    10

ans =
2
5
8

ans =
2     3
5     6
8     9

ans =
5     6
8     9```