how can i find same values in an array?

I have an array a, where

a=[303.1093
   94.5581
   86.6591
  108.1389
  303.1093
  107.4338
  138.6919
  106.8294
  108.1389
  149.3491
  187.8940
  125.0922
   96.7580
  303.1093
   75.9192
   96.2085
  118.8788
  303.1093
  303.1093
  303.1093]

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

[Meghana Dinesh]

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

[suchismita]

yes same values

Answer 1

[Star Strider]

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

-

[suchismita]

No its not working, all 303 should show as 1 and others as 0 for example,

       303.11            1
       94.558            0
       86.659            0
       108.14            0
       303.11            1
       107.43            0
       138.69            0
       106.83            0
       108.14            0
       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

[Stephen23]

It seems that this solution is not correct, as it misses 107.43 and 108.14 (rows 6 and 4). Surely these should be marked with 1's as (rounded) they match 106.83 and 108.14 respectively (rows 8 and 9, which may or may not be marked with 1's, depending on which results you read).

See my Answer for a solution that correctly identifies all matching values.

[Star Strider]

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]

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

Answer 2

[Stephen23]

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(:)]

   303.1093     1
    94.5581     0
    86.6591     0
   108.1389     1
   303.1093     1
   107.4338     1
   138.6919     0
   106.8294     1
   108.1389     1
   149.3491     0
   187.8940     0
   125.0922     0
    96.7580     0
   303.1093     1
    75.9192     0
    96.2085     0
   118.8788     0
   303.1093     1
   303.1093     1
   303.1093     1

[suchismita]

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

Answer 3

[Bhavini Sarkar]

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.

Answer 4

[Azzi Abdelmalek]

[ii,jj,kk]=unique(a,'stable')

[suchismita]

I wanna mark those same values as 1 and others 0, how can i do that