Question

Suppose I have a vector
A =

 3     5     3     3     2     2     4     2     6

I need to produce a new vector B that will contain all these values from the beggining vector A that will result in a unique number of n elements (suppose n=3, for the purpose of this example). The new vector should be B =

 3     5     3     3     2

since up to the fifth element of vector A we have 3 unique values(3,5,2).
Actual vectors are a lot larger, so I would rather need a general solution and preferably by avoiding a loop. Any ideas? Thanks in advance

Answer 1

You can use unique for this problem. However, be sure to use the 'stable' option.

A = [3     5     3     3     2     2     4     2     6]; 
n = 3; 

[x, id] = unique(A,'stable'); 

B = A(1:id(3))

This results in

B =

     3     5     3     3     2