如何在Matlab中使用条件提取矩阵的一部分 [英] How to extract a part of a matrix with condition in Matlab

问题描述

我有一些矩阵，我只想提取满足条件的一部分矩阵.

I have a sat of matrices and I want to extract only a part of the matrix that satisfy a condition.

例如:150x180矩阵的值从0到2.80，我只希望在1.66和1.77之间的值 我想将这些值保留在原始矩阵的原始位置范围内，并将另一个设置为零.

For example: values of the 150x180 matrix goes from 0 to 2.80 and I only want those between 1.66 and 1.77 I want to keep the values within the rang in their original location in the original matrix and set the other to zero.

有人可以帮我吗?

谢谢

推荐答案

您可以使用逻辑索引.首先，找到不满足您条件的A条目.接下来，使用A(idx)将其更改为0:

You can use logical indexing. First, find A entries that do not satisfy your conditions. Next, using A(idx) change them to 0:

% example matrix
A = 2.8*rand(150, 180);

% find entries meeting some criterion
idx = A<1.66 | A>1.77;
A(idx) = 0;

或更简单些，如Rody Oldenhuis所建议的，您可以将逻辑表达式直接包含在矩阵引用中:

Or simpler, as Rody Oldenhuis suggested, you can include the logical expression directly in the matrix reference:

A(A<1.66 | A>1.77) = 0;

这将产生更短，更简洁的代码，但不会产生更快的代码:MATLAB仍显式创建逻辑索引变量，但随后将其清除.

This yields a shorter and cleaner code, but not a faster code: MATLAB still explicitly creates the logical index variable, but clears it afterwards.

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