Need to match Data

Hello,

I like to match the entries in column 2 of matrix A to the reference numbers of B. I'm going to do that for large data sets. Code like follows does exactly what I want but will be to slow. Is there an intelligent function/way available to do that? Thanks a lot!

A = [2 3 5 7; 23 54 76 86]';

B = [1:7]';

j=1;

for i = 1:7

    if B(i,1) == A(j,1)

        B(i,2) = A(j,2);

        j = j+1;

    end

end

result: B =

     1     0
     2    23
     3    54
     4     0
     5    76
     6     0
     7    86

Answer 1

[Matt Fig]

B(A(:,1),2) = A(:,2)

[Matt Fig]

Johannes comments:

"Thank you. That was a bad example, my mistake.

What would be the solution for vectors like that:

A = [7 3 5 9; 23 54 76 86]';

B = [3:15]';"

[Matt Fig]

In that case:

A = [7 3 5 9; 23 54 76 86]';
B = [3:15]';
As = sortrows(A,1);
idx = ismember(B,As(:,1));
B(idx,2) = As(:,2)

Answer 2

[Andrei Bobrov]

A = [7 3 5 9; 23 54 76 86]';
B = [3:15]';
[a,b] = ismember(B,A(:,1));
B(a,2) = A(b(a),2);

Answer 3

[Johannes]

thank you all! My final solution is the following:

B(ismember(A),2)=A(ismember(A,B),2);

Works perfect and very fast.

Thank you again for your help.

Best, Johannes