Question

I have something like the following:

X = [1 5; 2 5; 3 7; 4 7; 5 2; 6 7];

X =

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

b = [1;4;6];

b =

 1
 4
 6

Is there a way to lookup the values (from X), input as b, to output the following:

b1 =

 1     5
 4     7
 6     7

Answer 1

If you’re sure that the values of b are within the range of X:

c = X(b,:);

or if the first column of X isn’t 1:N:

[~,idx]=ismember(b,X(:,1));
idx(idx==0)=[];
c = X(idx,:);