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📜  MATLAB-冒号表示法

📅  最后修改于: 2020-11-03 09:49:39             🧑  作者: Mango

Colon(:)是MATLAB中最有用的运算符之一。它用于创建向量，下标数组并指定迭代。

如果要创建包含1到10的整数的行向量，请编写-

现场演示
1:10

MATLAB执行该语句并返回包含1到10的整数的行向量-

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

如果要指定一个增量值而不是一个值，例如-

现场演示
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

让我们再举一个例子-

现场演示
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

您可以使用冒号运算符创建索引向量，以选择行，列或数组元素。

下表描述了此用途(让我们使用矩阵A)-

Format Purpose
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

创建一个脚本文件并在其中键入以下代码-

现场演示
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

运行文件时，它显示以下结果-

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