Assigning element of another array into another array based on index

I've stored the index of the elements of interest in an array, B, and would like to use the values in B to obtain the values of the elements in another array, A, at positions indicated in B.

e.g.

    A = [5 4 4 5 6 6 8 5 8 5 14 11 3 2 4 5];
    B = [1 2 4 8 10 12 16];
    for i = 1: length(B)
        if (A(B(i))== 5)
        idx = [idx,i];
    end
    end

form my understanding, i should be able to get idx = 1 4 8 10 16 However, what i am getting is idx = 1 5 10 15

I'm not sure what is the problem as the logic of the code seems right to me.

can i also check what is the difference between array and matrix?

Answer 1

[Matt J]

You don't really need a loop at all and can do the whole thing in one line,

    idx=B(A(B)==5)

[Matt J]

can i also check what is the difference between array and matrix?

Do you mean

   difference = B-A(B)

[Mich]

i tried this, but i had an error that says index exceed matrix dimensions. Actually i dont get this line, i dont understand why should it be B(...)== 5 when im looking for the value inside A.

[Matt J]

I never proposed anything that looks like B(...)== 5. The expression I wrote is B( A(B)==5 ).

I tested my proposal on your example data and it worked fine for me. So, whatever's causing your error, it's coming from something unposted.

[Mich]

hey i apologise for my mistake. my original code was way more complex and i simplified it to this, but the same variables were used, thus resulting in my initial confusion when i tried out your suggestion. i tried your suggestion again and it works! thanks alot!!

Answer 2

[vimala victor]

hi, i have one array RL=[1 13 11 14 25 37 53 29 75 81 66 10 98 15 33 44 77 88 20 49 1 3 4 2 5 1 2 2 3 4 2 1 5 2 3 1 2 4 3 3]; That is first row defines the index values and second row is the values of corresponding index.(Eg.for index value 1 the value is 1,index value 13 the value is 3...) and IM= 44 14 98 88 20 13 11 37 77 25 81 20; How can i extract the corresponding IM indexing Values from RL using indexing. please ,can anyone help me to clarify my doubt with how to define in matlab coding

[Guillaume]

Please, start your own question rather than highjacking a very ancient one.