How would I create my own 'unique' function without using the built in unique?

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Alexander
Alexander 2014-4-29
编辑： Sean de Wolski 2014-4-30
I understand that the built in Unique function is stating that whatever function you define as unique is the same data set but without repetitions.
should I create a function file such as
function[unique,c] = myuni_1(A)
rows(A)= size(A,1);
columns(A) = size(A,2);
and then proceed to define the rows and columns as itself? I'm a bit confused here.
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Alexander
Alexander 2014-4-29
My TA mentioned my professor may ask a question like this on my final exam and I would like to be prepared for anything. Also, my own curiosity is driving me to ask it.
I've looked at the function file on Matlab and it is a very long code. I'm curious if this is even possible with an alternative method that uses less code.
Jan
Jan 2014-4-30
编辑：Jan 2014-4-30
What exactly should your function do? Which types of input are expected? What is the 2nd output c? Please do not let us guess the details.
Notice that "rows(A)= size(A,1);" is no valid Matlab syntax.

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采纳的回答

Jan
Jan 2014-4-30
A short version:
function U = myUnique(A)
[As, SV] = sort(A(:));
UV(SV) = ([1; diff(As)] ~= 0); % [1, As(2:nA) - As(1:nA-1)];
U = A(UV);
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Alexander
Alexander 2014-4-30
works like a charm, i was using 3 different for loops and trying to sort each one by the size of A but got nothing.
Thank you friend!

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更多回答（2 个）

Walter Roberson
Walter Roberson 2014-4-29
Suppose you have two "bags", A and B. Start with A empty.
If B is empty, you are done and A holds the unique values. Otherwise, take one one item, C, out of B (removing it from B). Is there already a copy of C in A? If there is, then throw away C. Otherwise, add C to A. Now restart this paragraph.
Sean de Wolski
Sean de Wolski 2014-4-30
编辑：Sean de Wolski 2014-4-30
How about this?
x = [1 2 3 3 3 3 2 4 5];
[uv,ia] = intersect(x,x)

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