mapping between two different matrices

I have a matrix a=[1 2;3 4;5 6] and i have another matrix b=[1 2 3;1 2 3;1 2 3;1 2 3;1 2 3]. Now I want to map between two matrices in such a way that the first row of matrix 'a' is indicating the first column of matrix 'b'. Like, if I type [1 2], it should show [1;1;1;1;1]. If I type [3 4] it should show [2;2;2;2;2].

How to do that?

Answer 1

[Fangjun Jiang]

a=[1 2;3 4;5 6];
b=[1 2 3;1 2 3;1 2 3;1 2 3;1 2 3];
c=[1 2];
[~,index]=ismember(c,a,'rows');
b(:,index)

ans = 5×1

1 1 1 1 1

Answer 2

[Kevin Holly]

a=[1 2;3 4;5 6]

a = 3×2

1 2 3 4 5 6

b=[1 2 3;1 2 3;1 2 3;1 2 3;1 2 3]

b = 5×3

1 2 3 1 2 3 1 2 3 1 2 3 1 2 3

index = 3;
output = yourmap(a,b,index)

output = 5×1

2 2 2 2 2

index = 6;
output = yourmap(a,b,index)

output = 5×1

3 3 3 3 3

index = [1 2];
output = yourmap(a,b,index)

output = 5×2

1 1 1 1 1 1 1 1 1 1

function output = yourmap(a,b,index)
    
[row,column] = find(a==index);
output = b(:,row);

end

Answer 3

[Walter Roberson]

b(:,a(1,1))