Using loops to populate a vector

2016 2 16
1 个回答
回答已采纳
更新时间：2016 2 16
3 次查看（30 天）

0 个投票

Say I have a 3x2 matrix (A) that ranges from the numbers 1 through 5. The 3 rows equals 3 different sets of numbers. I have to use a loop to populate a vector (B) that is the size 3x1 (3 for each set). This vector will populate with the first number in each set (every number in the first column).
So if the matrix A =
2 3
1 1
5 4
the vector B should be
2
1
5
How would you use the loop function to do that?

请先登录，再回答此问题。

 采纳的回答

Moe_2015
Moe_2015 2016-2-16
编辑：Moe_2015 2016-2-16

0 个投票

If you really need to use a for loop, this is how you could do it.
for i=1:size(A,1)
B(i,1)=A(i,1);
end
However, a more efficient way would be:
B=A(:,1)

4 个评论
显示 2更早的评论 隐藏 2更早的评论

lauuser1
lauuser1 2016-2-16
These both work exactly how I want it, however when I suppress B in the loop function it ceases to show B at all. When I remove the suppression, it shows every step of populating B. This doesn't really affect my code, but would there be a way to fix that?
Image Analyst
Image Analyst 2016-2-16
Fix what? What does suppression mean to you? You mean having the value of B echo to the command window if you leave off the semicolon? If so, I'm still not sure what you want, or don't want, to see.
lauuser1
lauuser1 2016-2-16
What I am trying to fix is that I just want the final result of B rather than it echoing. I would like to see B in my command window as just one single fully populated 3x1 vector with no values of 0.
Image Analyst
Image Analyst 2016-2-16
Put B by itself after the loop to have it echo only the final B
for i=1:size(A,1)
B(i,1)=A(i,1); % Semicolon to suppress echo to command window.
end
% Print B to command window:
B

请先登录，再进行评论。

更多回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by