How to replace data in a matrix by comparing from another matrix?

I have a matrix A,

[1 5
 2 6
 3 6
 4 7
 5 6]

and I have another matrix B as

[1 2
 1 3
 1 4
 1 5
 2 3 
 2 4
 3 4 
 3 5
 4 5]

now i want to compare B with a and i want to replace 2nd column of B with A data for example,

[1 5
 1 5
 1 5
 1 5
 2 6 
 2 6
 3 6 
 3 6
 4 7]

in first column when there is 1 it will take the value of matrix A's second column data as 5 and when first column is having 2 it will take the value of 2 from matrix A.

please please help me.

Answer 1

[David Sanchez]

    for k=1:length(B)
        x = A(:,1)==B(k,1);
        B(k,2) = A(x,2);
    end

B =

       1     5
       1     5
       1     5
       1     5
       2     6
       2     6
       3     6
       3     6
       4     7

[suchismita]

thank u so much....

[Stephen23]

Andrei Bobrov's solution is much neater.

Answer 2

[Andrei Bobrov]

[lo,ii] = ismember(B(:,1),A(:,1));
out = B;
out(lo,2) = A(ii(lo),2);

[Stephen23]

Very nice solution, although it took me a while to realize that l0 is a variable. it looks similar to the number 10, especially when it is being used as an index.

If the nomenclature is clearer then this solution is much easier to read:

>> [ism,idx] = ismember(B(:,1),A(:,1));
>> out = B;
>> out(ism,2) = A(idx(ism),2)
out =
   1     5
   1     5
   1     5
   1     5
   2     6
   2     6
   3     6
   3     6
   4     7

[Andrei Bobrov]

Hi Stephen! I corrected..

[suchismita]

thank u so much.....

Answer 3

[Nobel Mondal]

Assuming, the 'a' matrix has unique values in the first column

for bRow= 1:size(b, 1)
  aRow = find(a(:,1)==b(bRow,1), 1);
    if ~isempty(aRow)
      b(thisrow,2) = a(aRow,2);
    end
end

[suchismita]

thank u so much....