Logical expression not working with loop and if statement

Question

Maxence Boels 2019-11-11

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/490409-logical-expression-not-working-with-loop-and-if-statement

评论： Walter Roberson 2019-11-11

I need an array with [1, 1, 0, 1, 0, 0, 1, 1, 0, 1]

N=10;
query_class=9;
n_candidate_class =  [9, 9, 4, 9, 5, 5, 9, 9, 5, 9];
imgout = zeros(1,N); 
for n = 1:N
    for c = 1:N
        if query_class == n_candidate_class(n)
                imgout(c) = 1;
        else
                imgout(c) = 0;
        end
    end
end

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Maxence Boels 2019-11-11

Thank you ! Much simpler than I thought.

Do you know what was going wrong in my query?

Walter Roberson 2019-11-11

You overwrite each imgout(c ) for each different n value, so you are only getting the result as-if you had run with n=N . You want to be comparing corresponding values, not each one to each other.

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Answer 1

Ankit 2019-11-11

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https://ww2.mathworks.cn/matlabcentral/answers/490409-logical-expression-not-working-with-loop-and-if-statement#answer_400893

编辑：Ankit 2019-11-11

Hello Maxence Boels,

this is due to the inner for loop, which is causing problem. for n =1, the inner loop changes its values from 1 to 10, and compares query_class(whose value is 9) to n_candidate_class(1) which is also 9. Hence it return [1,1, 1,1,1,1,1,1,1,1] for the first iteration of n.

N=10;
query_class=9;
n_candidate_class =  [9, 9, 4, 9, 5, 5, 9, 9, 5, 9];
imgout = zeros(1,N); 
for n = 1:N
    if query_class == n_candidate_class(n)
        imgout(n) = 1;
    else
        imgout(n) = 0;
    end  
end