Loop is not reading from the first value in the array?

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Jasmine Karim 2018-8-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414120-loop-is-not-reading-from-the-first-value-in-the-array

评论： Jasmine Karim 2018-8-9

I have a loop that is transferring data between two arrays, however, I'm not sure why it is not reading from the very first and last values. The first array (arrayA) looks like:

    {'7'}    {'ans'}    {[1]}
    {'7'}    {'ans'}    {[2]}
    {'7'}    {'ans'}    {[3]}

second array (arrayB) looks like:

    {'7'  }    {[101]}    {[1]}
    {'ans'}    {[278]}    {[1]}
    {'7'  }    {[299]}    {[2]}
    {'ans'}    {[300]}    {[2]}
    {'7'  }    {[432]}    {[3]}
    {'ans'}    {[467]}    {[3]}

With the following loop, IF the value in arrayA{a,3} matches that in arrayB{b,3}, i want the FIRST matching value to appear in arrayB{b,4} and the SECOND matching value to appear in arrayB{b,5}.

for a = 1:length(arrayA)
            for b = 1:length(arrayB)
                if arrayA{a,3}==arrayB{b,3}
                    arrayA{a,4} = arrayB{b,2};
                    arrayA{a,5} = arrayB{(b+1),2};
                end
            end
        end

Right now, it looks like:

    {'7'}    {'ans'}    {[1]}    {[278]}    {[299]}
    {'7'}    {'ans'}    {[2]}    {[300]}    {[432]}
    {'7'}    {'ans'}    {[3]}    {[467]}    {[467]}

What I would like however would be:

    {'7'}    {'ans'}    {[1]}    {[101]}    {[278]}
    {'7'}    {'ans'}    {[2]}    {[299]}    {[300]}
    {'7'}    {'ans'}    {[3]}    {[432]}    {[467]}

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Rik 2018-8-8

What is the goal of this code? What are you trying to achieve? Also, (b-1)+1 is just b, so is that a typo?

I think I would use ismember(arrayA,arrayB) to get a list of valid positions, but that is just a gut feeling without knowing a bit more about your goal and what sort of data to expect.

Jasmine Karim 2018-8-9

Thanks for asking for clarification, I have posted a sample dataset to better explain what I am trying to achieve

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Answer 1

Fangjun Jiang 2018-8-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414120-loop-is-not-reading-from-the-first-value-in-the-array#answer_332172

It is because third column in B has duplicated values. For example, the result of the first loop (b=1) in the "for b = 1:length(arrayB)" loop is over-written by the second loop (b=2)

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Fangjun Jiang 2018-8-9

在 MATLAB Online 中打开

for a = 1:size(arrayA,1)
            Col=3;
            for b = 1:size(arrayB,1)
                if arrayA{a,3}==arrayB{b,3}
                   Col=Col+1;
                   arrayA{a,Col} = arrayB{b,2};
                end
            end
end