如何用标量替换向量的所有元素

问题描述

我有一个向量(或数组)

I have a vector (or array)

A = [2 3 4]

我想用标量值4替换每一行的所有元素.我有代码:

I want to replace all elements of each row with a scalar value of 4. I have the code:

for ii = 1: size(A, 1) A(ii,:) = 4end

for ii = 1: size(A, 1) A(ii,:) = 4end

这将返回A = [4 4 4].如何获得1x1矩阵:A = [4]而不是1x3矩阵?

This returns A = [4 4 4]. How can i obtain a 1x1 matrix: A = [4] rather than the 1x3 matrix?

非常感谢.

推荐答案

谢谢大家的评论.尽管它说我应该分配一个标量，但没有说我如何有效地做到这一点.这是有效的方法:

Thank you guys for your comments. Although it says i should assign a scalar, it didn't say how i could do that effectively. Here is what works:

A = [2 3 4; 1 3 2];

for ii = 1: size(A, 1)
   B(ii,:) = A(ii,3)  
end

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