MATLAB: Efficient way of setting up a substitution table

Question

I have a straightforward problem but I am looking for a more efficient way to set it up. The data set I am using is very large, but for example sake: I have 2 nx2 matrices. The first has 1 column of index values and the other of random values

    A=
    1 5
    2 3
    3 1
    4 5
    5 2

The second has a list of random substitutions:

    1 1.24
    2 2.67
    3 3.88
    4 4.22
    5 5.23

I would like to assign the substitutions from matrix B to the second column of Matrix A so it would read:

    1 5.23
    2 3.88
    3 1.24
    4 5.23
    5 2.67

I have tried using changem but I am wondering what is the best way to go about this. Thanks in advance

Answer 1

[tf, idx] = ismember(A(:,1), B(:,1));
A(tf,2) = B(idx(tf),2);