matlab - 从矩阵中选择一系列值并交换它们

Question

我有一个矩阵，我想选择一系列元素。例如，我想选择所有低于 182 的元素并交换/更改它们。有人知道在 matlab 中执行此操作的简单方法或命令吗？

谢谢

Answer 1

Since you say "swap", I understand you mean a vector, not a matrix. You can do it as follows:

x = [ 1 34 66 22 200 55 301 ]; % data
[ values, ind ] = find(x<182);
x(ind) = x(ind(end:-1:1));

To simply replace them by another value such as NaN, do as follows. Note that this works also for matrices:

x = [ 1 34 66 22 200 55 301 ]; % data
x(x<182) = NaN;

Answer 2

这些事情通常可以通过逻辑索引来完成：

A = randn(1,100);
B = randn(size(A));
test = (A>1|A<0);   % For example, values that are greater than 1 or less than 0
A(test) = B(test);

或另一个例子：

A = randn(1,100);
test = (A>1|A<0);
A(test) = randn(1,nnz(test));

或其他：

A = randn(1,100);
A(A>1|A<0) = NaN;

Answer 3

您可以像这样使用循环：

   for i = 1:length(matrix(:,1))
        for j = 1:length(matrix(1,:))
            if matrix(i,j) < 182
               matrix(i,j) = NaN;
            end
        end
    end