How to construct an array from two arrays of different sizes using conditional replacement of elements?

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Emerson De Souza on 15 Oct 2012
Hi, I have two arrays A and B as below
where
A=
1
2
3
4
5
6
7
8
9
10
and
B=
1 4
3 10
6 15
8 17
9 59
Goal: I want to construct an array C with the same length as A. The elements of C equals the elements of the second column of B if the elements of the first column of A and the elements of the first column of B are equal. Otherwise, the elements of C is not available (NaN)
Thus, C should look like below:
C=
1 4
2 NaN
3 10
4 NaN
5 NaN
6 15
7 NaN
8 17
9 59
10 NaN
I tried the following command lines:
C=zeros(size(A));
for i=1:numel(A);
for j=1:numel(B);
if A(i)=B(j);
C(i)=B(j,2);
else
C(i) = NaN;
end;end;
but had no success yet. I wonder if someone could help me to correct the mistakes I have done or suggest something else that works.
I thank you in advance for you help
Emerson
Emerson De Souza on 25 Oct 2012
Thank you Andrei,
these command lines are exactly what I need for general situations.
Emerson

Azzi Abdelmalek on 15 Oct 2012
Edited: Azzi Abdelmalek on 15 Oct 2012
C=nan(numel(A),1)
for k=find(ismember(A,B(:,1))==1)
C(k)=B(find(B(:,1)==A(k)),2)
end
Emerson De Souza on 25 Oct 2012
Hi Matt Fig,
I absolutely agree with you, I should have thought more in detail before asking. Now reformulating the problem:
1)A and B are arrays with arbitrary number of rows and columns. Their values are elements of Real Numbers (exclude only complex numbers).
2)The array C is constructed as follows:
(i) The first column of C is identical with the first column of A,
(ii) The second column of C is initially filled with NaN,
(iii) Whenever there is a match between one element of the first column of A with one element of the first column of B, then the element of the second column of C equals the value of the element of the second column of B.
Fortunately, Andrei understood between my lines above and fixed the problem. Thank you anyways for your attention
Emerson