Extracting Rows of a Matrix

Question

A M 2017-3-27

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https://ww2.mathworks.cn/matlabcentral/answers/332219-extracting-rows-of-a-matrix

评论： Star Strider 2024-2-13

I have a matrix 'A' of size 8*5. How to extract the first 4 rows of this Matrix.

 A =  90.6848   72.5836   54.4646   36.3276   18.1728
7018   79.8089   59.8924   39.9521   19.9880
7026   88.6271   66.5192   44.3788   22.2058
4195   99.6278   74.7902   49.9066   24.9766
9931  113.7314   85.4017   57.0036   28.5365
3005  132.4561   99.5049   66.4459   33.2780
6559  158.4928  119.1482   79.6196   39.9045
4805  197.0868  148.3494   99.2610   49.8139

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SURESH KUMAR 2023-4-6

very simple

Please follow this step

Matrix_Column= A(1:4,:);

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Answer 1

Star Strider 2017-3-27

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https://ww2.mathworks.cn/matlabcentral/answers/332219-extracting-rows-of-a-matrix#answer_260597

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First_Four_Rows = A(1:4,:);

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A M 2017-3-27

Sorry for the confusion. Like all those rows whose first value is greater than 99 and less than 140, i.e. rows 2, 3 and 4

Star Strider 2017-3-28

在 MATLAB Online 中打开

No worries. I needed to understand what you want.

This works:

Extracted = A((A(:,1)>99) & (A(:,1)<140),:);

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Answer 2

John BG 2017-3-27

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With

A(1:4,:)

you still get a 2D matrix as result

If you want to pull elements and get a 1D vector then

A([1:4 1:end])

same elements, lined up, 4x5 now 1x44

if you find these lines useful would you please mark my answer as Accepted Answer?

To any other reader, if you find this answer of any help, please click on the thumbs-up vote link,

thanks in advance for time and attention

John BG

<mailto:jgb2012@sky.com jgb2012@sky.com>

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Jan 2017-3-28

If the original matrix has the dimension [8 x 5] and A M wants to extract 4 rows, how could the result be a [1 x 44] vector? Your "1:end" means "1:numel(A)" here and is not useful.

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