MATLAB: Find unique rows of cell array

cell arraysduplicatesindexingrowsunique

I have a cell array as attached. I can see that rows 3 and 4 are repeated, so I would like to keep only the first occurrence of this repetition. I have tried a few things, but calling unique(x, 'rows') doesn't work on cell arrays and each row is a different size, so i have found a few issues when trying to cell index.

Thankyou.

Best Answer

This is possibly more efficient than the other solutions:

[r1, r2] = ndgrid(1:size(matching__, 1));
duplicates = any(triu(arrayfun(@(r1, r2) isequal(matching__(r1, :), matching__(r2, :)), r1, r2), 1))
matching__(duplicates, :) = []

In your example, only rows 3 and 5 are identical.

Related Solutions

MATLAB: How to get the indices of non-empty cells from a cellstr array

Here is an example

x = {1,[]}
find(~cellfun(@isempty,x))

MATLAB: How to check if a certain matrix is one of the cells of the cell array

Try it with a simple loop:

A = {[1 2;3 4] [2 2;3 3] [1 1;2 2]};
b = [1 2;3 4];
isInCell(A, b)
function R = isInCell(A, b)
R = false;
for k = 1:numel(A)
  if isequal(A{k}, b)
    R = true;
    return;
  end
end

ismember and similar functions to not handle cells except for cell strings. See also: https://www.mathworks.com/matlabcentral/answers/352144-unique-on-a-nx1-cell-array-with-different-length-vectors-per-cell

Alternatively:

R = any(cellfun(@(x) isequal(x, b), A))

This is much nicer, but slower: For a {1 x 1e5} cell containing rand(3) matrices, searching for the last element takes 0.13 sec with the loop method and 0.89 sec with cellfun. The earlier the matching matrix appears, the higher is the advantage for the loop.

Best Answer

Related Solutions

MATLAB: How to get the indices of non-empty cells from a cellstr array

MATLAB: How to check if a certain matrix is one of the cells of the cell array

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