在MATLAB中选择矩阵的对角元素 [英] Select Diagonal Elements of a Matrix in MATLAB

问题描述

在MATLAB中考虑以下矩阵：

Consider the following matrix in MATLAB:

01 02 03 04 05 06 07

01 02 03 04 05 06 07

08 09 10 11 12 13 14

08 09 10 11 12 13 14

15 16 17 18 19 20 21

15 16 17 18 19 20 21

22 23 24 25 26 27 28

22 23 24 25 26 27 28

29 30 31 32 33 34 35

29 30 31 32 33 34 35

36 37 38 39 40 41 42

36 37 38 39 40 41 42

43 44 45 46 47 48 49

43 44 45 46 47 48 49

我必须为图像的7 x 7窗口（移动）生成方向变异图。我将使用 nlfilter 进行处理，但是为了开发函数来计算变量图，我无法决定如何在窗口中选择元素。例如，当我考虑中心值25时，在EW方向上我只需要考虑25,26,27和28;在NE方向上，当选择的滞后时间为1时，我只需要考虑25,19,13和07.是否有任何标准命令可以这样做？

I have to generate directional variograms for such 7 x 7 windows(moving) of an image. I will use nlfilter for the process but for developing the function to calculate variograms I am not able to decide how to select elements in the window. For example when I consider the central value 25, in EW direction I have to consider only 25, 26, 27 and 28; in NE direction I have to consider only 25, 19, 13 and 07 when the lag chosen is 1. Is there any standard command to do so?

推荐答案

您可以编写一个函数来轻松获取这些元素：

You can write a function to get these elements yourself easily:

A = [01 02 03 04 05 06 07
     08 09 10 11 12 13 14
     15 16 17 18 19 20 21
     22 23 24 25 26 27 28
     29 30 31 32 33 34 35
     36 37 38 39 40 41 42
     43 44 45 46 47 48 49];

c = (size(A)+1)/2;
EW = A(c(1),c(2):end)
NE = diag(A(c(1):-1:1,c(2):end))

只需在函数（最好是m文件）中编写此代码，执行操作并将结果传回。

Just write this code in a function (preferably an m-file), perform your operation and pass the result back.

diag 函数返回矩阵的对角元素（或传递向量时返回对角矩阵） 。

The diag function returns the diagonal elements of a matrix (or returns a diagonal matrix when passed a vector).

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