how can i find same values in an array?

Question

suchismita 2016-2-5

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回答： Bhavini Sarkar 2016-9-17

I have an array a, where

a=[303.1093
5581
6591
1389
1093
4338
6919
8294
1389
3491
8940
0922
7580
1093
9192
2085
8788
1093
1093
1093]

then i wanna do

b=round(a);

In b I want to find the positions who are having same values and I want to mark those value as 1 and others 0.

please help me.

Thank you

-- Suchi

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Meghana Dinesh 2016-2-5

编辑：Meghana Dinesh 2016-2-5

How much "similar"? Or do you mean "same"?

suchismita 2016-2-5

编辑：suchismita 2016-2-5

yes same values

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Answer 1

Star Strider 2016-2-5

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编辑：Star Strider 2016-2-5

在 MATLAB Online 中打开

The unique function will obviously provide the information you want, but ‘the positions who are having similar values’ is less clear. I believe the au (unique values in ‘a’) and ‘ic’ values (the indices in ‘a’ that correspond to them) is what you want:

[au,ia,ic] = unique(round(a),'stable')

EDIT —

‘I wanna mark those same values as 1 and others 0’

I believe this does what you want:

[au,ia] = unique(round(a),'stable');
Same = ones(size(a));
Same(ia) = 0;
Result = [a Same]
Result =
       303.11            0
       94.558            0
       86.659            0
       108.14            0
       303.11            1
       107.43            0
       138.69            0
       106.83            1
       108.14            1
       149.35            0
       187.89            0
       125.09            0
       96.758            0
       303.11            1
       75.919            0
       96.209            0
       118.88            0
       303.11            1
       303.11            1
       303.11            1

-

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Star Strider 2016-2-5

I wasn’t certain what you wanted. I thought you only wanted to flag the repeated values, other than the first occurrence. Since this now seems to be resolved, I’ll not pursue it further.

Stephen23 2016-2-5

Good point about the "first occurrence". This did not occur to me, and the original question is ambiguous on this point.

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Answer 2

Stephen23 2016-2-5

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在 MATLAB Online 中打开

This identifies all matching rounded values, unlike the accepted answer:

b = round(a(:));
c = bsxfun(@eq,b,b.');
x = any(tril(c,-1)|triu(c,1),1);
[a(:),+x(:)]
1093     1
5581     0
6591     0
1389     1
1093     1
4338     1
6919     0
8294     1
1389     1
3491     0
8940     0
0922     0
7580     0
1093     1
9192     0
2085     0
8788     0
1093     1
1093     1
1093     1

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suchismita 2016-2-6

i want to accept your answer but i dont how to unlike the already accepted answer?

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Answer 3

Bhavini Sarkar 2016-9-17

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To find the duplicate elements of an array, first you should sort array . After sorting all duplicate elements will aggregate in adjacent positions. Now using a for loop , traverse sorted array and compare adjacent elements. If adjacent elements are equal then you found one duplicate element of array . We can also find duplicate elements of an array in linear time using some extra space.