How to find unique elements in a vector without using unique or find?

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Trevor Badji 2016-10-23

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https://ww2.mathworks.cn/matlabcentral/answers/308694-how-to-find-unique-elements-in-a-vector-without-using-unique-or-find

编辑： Image Analyst 2017-12-11

采纳的回答： Massimo Zanetti

I have A=randi(100,1,100); How can I find unique values in array and show them without using unique() and find() .

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John D'Errico 2016-10-24

Yes. It CAN be done using basic MATLAB statements.

For example, using sort, then diff and find will make it absolutely trivial. And if you cannot use unique, then sort, diff and find are off limits too.

But this is homework. You need to do your homework. There is simply no reason for this question under any other circumstances. It was assigned to you, for you to learn. If we doit for you then you learn nothing but how to get others to do your work.

Rena Berman 2017-1-20

编辑：Image Analyst 2017-12-11

在 MATLAB Online 中打开

(Answers Dev) Restored Question.

I have

A=randi(100,1,100);

How can I find unique values in array and show them without using unique() and find() .

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Answer 1

Massimo Zanetti 2016-10-23

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https://ww2.mathworks.cn/matlabcentral/answers/308694-how-to-find-unique-elements-in-a-vector-without-using-unique-or-find#answer_240258

编辑：Massimo Zanetti 2016-10-23

在 MATLAB Online 中打开

Use an histogram based approach (works only for positive integers)

%get M random numbers from 1 to N
M=10; N=25; 
A=randi(N,1,M)
%find unique values
x=1:N;
unique_vals = x(logical(accumarray(A',1,[N,1])))

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Trevor Badji 2016-10-24

This works thanks however I need to solve this problem without using any matlab functions . Can we do this with using for or if ?

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Answer 2

Thorsten 2016-10-24

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https://ww2.mathworks.cn/matlabcentral/answers/308694-how-to-find-unique-elements-in-a-vector-without-using-unique-or-find#answer_240430

编辑：Thorsten 2016-10-24

在 MATLAB Online 中打开

You can do this with for and if:

suppose you have the numbers in x
and want to generate the unique numbers in xu
pick the first number of x, this is your first unique number in xu
now run through all the number in x
    check if it is in xu
     if so, proceed with the next number of x
    else, add the number to your unique numbers x

Voilá

This is a possible algorithm, and it is up to you to implement it, to learn something.

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Trevor Badji 2016-10-24

I got the algorithm thanks for the reply . But Im new at matlab I do not know how to add the number to xu for example . I can write this code by C++ however I am having trouble in matlab . I get errors mostly

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