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

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]}

[Rik]

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]

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

Answer 1

[Fangjun Jiang]

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)

[Jasmine Karim]

is there a way to edit the loop so it doesn't run into this issue?

[Fangjun Jiang]

You have to tell first, how to deal (non programming) with this case (duplicated value in third column of B)

[Jasmine Karim]

the FIRST value in the second column of B should go in the 4th column of A, and the SECOND (duplicated) value in B should go in the 5th column of A.

[Fangjun Jiang]

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

Note that size() is better than length() for your case.

[Jasmine Karim]

Ah, I had not used size instead of length before. Thank you!