MATLAB: Is it possible to sort an array by making the repeated elements in the last

MATLABrepeated elementssorting

Greetings.

Consider a vector A = [-2 -2 -1 3 3], is it possible to sort this vector (a generalized method) to [-1 -2 -2 -3 -3]?

The only thing that matters is that the repeated elements are in the last, it doesn't matter what way the repeated elements themselves are sorted (for example, [-1 -2 -2 -3 -3] or [-1 -3 -3 -2 -2] are fine) I just want the distinct value to be on the left before any repeated value.

Thank you in advance,

M. Ayoub

Best Answer

>> A = [-2,-2,-1,3,3,3,9,9,0,99]
A =
   -2   -2   -1    3    3    3    9    9    0   99
>> [cnt,idx] = histc(A,unique(A));
>> [~,idy] = sort(cnt>1);
>> [~,idz] = ismember(idx,idy);
>> [~,ids] = sort(idz);
>> B = A(ids)
B =
   -1    0   99   -2   -2    3    3    3    9    9

And

>> A = [-1,-1,-3,-5,-5]
...
B =
  -3  -5  -5  -1  -1

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MATLAB: How to modify a matrix to change the entries >=0 and multiply it by 5 AND to change the entries <0 and add 2 to those entries

Start with "If an entry in B is greater than or equal to zero": You can either run a loop over all elements of B or use "logical indexing":

% Linear indexing:
for k = 1:numel(B)
   if B(k) >= 0
     ...
   end
end

Or two indices for rows and columns:

for r = 1:size(B, 2)
  for c = 1:size(B, 1)
    if B(r, c) >= 0
       ...
    end
  end
end

Or "logical indexing":

index = (B >= 0);
disp(B(index))

Now try to use this to modify B. Use the mentioned terms to search in the documentation and in the internet.

MATLAB: Question about the sign

Use sign function

In your case you can use

   H(se+1,:)=2*H(se+1,:)

Best Answer

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MATLAB: How to modify a matrix to change the entries >=0 and multiply it by 5 AND to change the entries <0 and add 2 to those entries

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