How to find rows that contain value in another column vector

Let say I have matrix X as follows

X = 
1 2 3
1 4 5
1 6 7
2 8 9
2 10 11
3 12 13
3 14 15
3 16 17
4 18 19
4 20 21
5 22 23
5 24 25

and column vector Y

Y=
2
4
5

So, I want to create a matrix where based on values in Y that has the same value of Column 1 of X

So,

Z=
2 8 9
2 10 11
4 18 19
4 20 21
5 22 23
5 24 25

Answer 1

[KSSV]

Read about ismemebr

X = [1 2 3
1 4 5
1 6 7
2 8 9
2 10 11
3 12 13
3 14 15
3 16 17
4 18 19
4 20 21
5 22 23
5 24 25];
Y=[2
4
5] ;

[ia,ib] = ismember(X(:,1),Y) ;

iwant = X(ia,:)

Answer 2

[Walter Roberson]

Z = X(ismember(X(:,1), Y), :);

provided that the original order from X is acceptable.

That is, suppose that Y = [2; 5; 4], then would you need the Z to be in a different order?

If the X values had not happened to be in order by column 1, then would you still need the output to be in the same order as the Y values, or could they be in whatever order they were in in X ?