How to call vector in matrix with condition

Let's say:

A=[7 2 3 50;4 5 6 15;1 8 9 20;1 1 1 30]

A= 7     2     3    50
   4     5     6    15
   1     8     9    20
   1     9     8    30
B=[1; 7]

B=[1      
   7]

Question: I wanna call only vector in column 4 of matrix A with the condition is: the value of matrix B have the same value of vector in 1st column of matrix A?

I hope the result like that:

result=[20; 30;50]
result=[20
        30
        50]

i try :

    result=A(ismember(A(:,1),B,'rows'),4);

But, result=[50; 20;30]% it is not in order of vector in matrix B ????

Answer 1

[Bruno Luong]

[tf,loc] = ismember(A(:,1),B);
r = sortrows([loc(tf),A(tf,4)],1);
r(:,2)

ans =

    20
    30
    50

Answer 2

[Jan]

[m, loc] = ismember(A(:,1), B);
R      = A(m,4);
[~, q] = sort(loc(m));
R      = R(q)

[Jan]

Sorting loc(m) and using the index is exactly what happens inside sortrows([loc(m), A(m,4)], 1), so this answer is almost identical to Bruno's.

Answer 3

[KSSV]

k = A(A(:,1)==B(1),4)  
l = A(A(:,1)==B(2),4)

Or

[idx,ia] = ismember(A(:,1),B)
iwant = A(idx,4)

[ha ha]

Thanks @KSSV

But, i follow your code, and the result is :

result=[50; 20;30]% it is not in order of vector in matrix B ????

It is NOT what I want(bz it is not in order).