Assigning element of another array into another array based on index

2014 10 29
2 个回答
回答已采纳
更新时间：2018 5 16
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0 个投票

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?

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 采纳的回答

Matt J
Matt J 2014-10-29
编辑：Matt J 2014-10-29

0 个投票

You don't really need a loop at all and can do the whole thing in one line,
idx=B(A(B)==5)

4 个评论
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Matt J
Matt J 2014-10-29
can i also check what is the difference between array and matrix?
Do you mean
difference = B-A(B)
Mich
Mich 2014-10-29
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
Matt J 2014-10-29
编辑：Matt J 2014-10-29
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
Mich 2014-10-29
编辑：Mich 2014-10-29
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!!

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更多回答（1 个）

vimala victor
vimala victor 2018-5-16

0 个投票

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

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