i want to extract rows from a matrix

5 次查看（过去 30 天）
Mahmoud Chawki
Mahmoud Chawki 2022-5-16
回答： Animesh Gupta 2022-6-8
i have a matrix that the number of rows are always even.
i want a code that extracts 2 rows and put them together
for example:
s=[Row1;Row2;Row3;Row4;Row5;Row6]
s is a matrix that has six rows
i want to extract row 1 and row 2, put them together.
row 3 and row 4, put them together.
row 5 and row 6, put them together.
how can i achieve this?
  5 个评论
显示 3更早的评论
Mahmoud Chawki
Mahmoud Chawki 2022-5-16
The problem is that this matrix varies in rows, it depends on a number which is number of plies if number of plies is 3 this matrix will have 6 rows if number of lies is 4 this matrix will have 8 rows so you see it is alternating and depends on the input that the user uses
DGM
DGM 2022-5-16
编辑：DGM 2022-5-16
Ran in:
You're going to have to define the factors either way, so the fact that the array may differ in size doesn't matter. The problem is that we still don't know what you're actually trying to multiply with what and what the final output is.
For instance, if you want every pair of rows multiplied by a scalar:
A = [7 9 6; 9 1 5; 2 9 6; 9 2 1; 4 7 5; 7 8 8]
A = 6×3
7 9 6 9 1 5 2 9 6 9 2 1 4 7 5 7 8 8
k = repelem(1:size(A,1)/2,1,2).'
k = 6×1
1 1 2 2 3 3
B = A.*k
B = 6×3
7 9 6 9 1 5 4 18 12 18 4 2 12 21 15 21 24 24
Note that this example works regardless of how many rows A has. Generating k as a simple linear ramp is probably not what you want, but you haven't said what you want the factors to be.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Animesh Gupta
Animesh Gupta 2022-6-8
Hi,
It is my understanding that you want to extract adjacent rows of a matrix.
You may refer the following code snippet that demonstrates a procedure to extract adjacent rows.
mat = rand(10,5); % creating an array using rand method
disp(mat);
num_of_rows = size(mat,1); % using size method to get the dimensions of matrix along axis 1
new_mat = [];
for i = 1:num_of_rows-1
if mod(i,2) == 1
new_mat = cat(3, new_mat, [mat(i,:); mat(i+1,:)]); % using cat method to append along the 3rd dimension of the new matrix
end
end
% You can access the individual 2d sub-arrays as:
disp(new_mat(:,:,1));
disp(new_mat(:,:,2));
I hope it helps.

类别

在 Help Center 和 File Exchange 中查找有关 Creating and Concatenating Matrices 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