Eliminate rows from an array

Question

José Santos Pérez Leal 2021-6-12

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评论： José Santos Pérez Leal 2021-6-12

Hi everyone

How can I cut a 31450X1 array in order to obtain the same array with a dimension of 15725X1, eliminating the second half of rows from the original array? The array is a variable I'm working with, but I can't solve that problem. I tried it creating the next code:

LEN=length(data3);

for x=1:LEN

if x>(LEN/2)

ROW=LEN;

data3(ROW,:)=[];

end

Where data3 is the 31450X1 array, but the matrix index is out of range for deletion

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Answer 1

Image Analyst 2021-6-12

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To eliminate the "second half of rows" (like you asked) from your column vector, do this:

midRow = ceil(length(data3) / 2);
data3 = data3(midRow : end);

To eliminate every other row, do this:

evenRows = data3(2:2:end); % Extract even numbered rows only.
oddRows = data3(1:2:end); % Extract odd numbered rows only.

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José Santos Pérez Leal 2021-6-12

Thank you very much!!! I will analize it in order to understand your method, thank you!!

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Answer 2

Mouhamed Niasse 2021-6-12

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Hello, this is what you tried to achieve:

data3(1+length(data3)/2:length(data3),:)=[];

Try to run below example. Hope it helps you understand.

data3=ones(31450,1); % data3 initialized as row vector of size 31450x1
size(data3)
data3(1+length(data3)/2:length(data3),:)=[]; % Eliminate second half of rows
size(data3)