Check an entire matrix against each value of another matrix

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EYKL 2022-1-14

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https://ww2.mathworks.cn/matlabcentral/answers/1629050-check-an-entire-matrix-against-each-value-of-another-matrix

评论： Jon 2022-1-14

采纳的回答： Jon

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Dear all,

I have the following code;

I want to check matrix b against each value of matrix a, and extract values in matrix b based on a condition.
The condition when delta 1 == 0, the value of matrix b corresponding to 0 is extracted into c.

However, I am getting an error Index in position 1 exceeds array bounds (must not exceed 1) in the line below. I have 2 questions:

Why is this error happening?
Is there another way to accomplish this without using loops?

Thank you.

a = [4 3];
b = [1 4.2 5 6 7 3.2];
c = zeros(size(a));
for i = 1:length(a)
    delta1(i,:) = abs((b-a(i))/a(i));
    for j = 1:length(delta1)
        if delta1(i,j) < 0.3
           c(i) = b(i,j);               % This line
        end
    end
end

采纳的回答

Jon 2022-1-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1629050-check-an-entire-matrix-against-each-value-of-another-matrix#answer_874690

编辑：Jon 2022-1-14

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If I understand what you are looking for, I think this will do it in a very simple way

c = intersect(a,b)
>> a = [4 3];
b = [1 4 5 6 7 3];
c = intersect(a,b)
c =
     3     4

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Jon 2022-1-14

编辑：Jon 2022-1-14

在 MATLAB Online 中打开

Ooops, that last line should be

c = b(any(delta < 0.3))
c =
    4.2000    5.0000    3.2000

if you want to list the values that match out of b instead of the ones out of a (as in code above)

Jon 2022-1-14

You should also check out the MATLAB function ismembertol https://www.mathworks.com/help/matlab/ref/ismembertol.html which is pretty much purpose built for the operation you are trying to perform, but the error tolerance is a little different. If you are comfortable with their way of computing the tolerance you can use this directly

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