How can I remove duplicates in an array but keep the same order?

Question

I have this cell array in MATLAB:

y = { 'd' 'f' 'a' 'g' 'g' 'a' 'w' 'h'}

I use unique(y) to get rid of the duplicates but it rearranges the strings in alphabetical order:

>> unique(y)

ans =

'a'    'd'    'f'    'g'    'h'    'w'

I want to remove the duplicates but keep the same order. I know I could write a function do do this but was wondering if there was a simpler way using unique to remove duplicates while keeping the same order just with the duplicates removed.

I want it to return this:

>> unique(y)

ans = 

'd'    'f'    'a'    'g'    'w'    'h'

Answer 1

Here's one solution that uses some additional input and output arguments that UNIQUE has:

>> y = { 'd' 'f' 'a' 'g' 'g' 'a' 'w' 'h'};  %# Sample data
>> [~,index] = unique(y,'first');        %# Capture the index, ignore the actual values
>> y(sort(index))                           %# Index y with the sorted index

ans = 

    'd'    'f'    'a'    'g'    'w'    'h'

Answer 2

In MATLAB R2012a, a new order flag was added:

>> y = {'d' 'f' 'a' 'g' 'g' 'a' 'w' 'h'};
>> unique(y, 'stable')
ans = 
    'd'    'f'    'a'    'g'    'w'    'h'