MATLAB: Finding the set of unique values for another set of unique values

uniqueunique for each uniquevalue

hi everyone,

i have a dataset of which the first column contains buyers ID', the second column has a certin index, i need an output that shows what are the indeces associated with each unique buyer ID, for example: if i have a set like this:

1 3

1 4

2 5

2 4

3 1

3 7

3 9

M = [ 1,3;1,3;1,4;2,5;2,4;3,1;3,7;3,7;3,7;3,9];

i want an output in the form of

1 [3 4]

2 [5 4]

3 [1 7 9]

can anyone please help me?

Best Answer

i am looking for an array type [...] can it be filled with NaN or zeros?

NaN is probably wiser.

M = [ 1,3;1,3;1,4;2,5;2,4;3,1;3,7;3,7;3,7;3,9];
Mdedup = unique(M, 'rows');  %remove duplicate rows.
[id, ~, sub] = unique(Mdedup(:, 1)); %list of unique IDs and corresponding location
maxcount = max(accumarray(sub, 1));  %get max of histogram of IDs = width of matrix to create
result = [id, cell2mat(accumarray(sub, Mdedup(:, 2), [], @(v) {[v.', nan(1, maxcount - numel(v))]}))]

Related Solutions

MATLAB: Sum of Multiplication of column values in cell array

It is much easier to work with multi-dimensional arrays instead of nested cells. The cell arrays require loops for numerical operations, such that they are a bad choice, if you want to avoid loops. But you can convert the data:

Result = cell(size(x));
for k = 1:numel(x)
  Result{k} = y{k} * cat(1, x{k}{:});
end

The actual calculation is a simple matrix multiplication.

MATLAB: 1D array combinations

This will generate a cell array of all combinations of all possible lengths:

C = cell(size(A));
for k = 1:numel(C)
    C{k} = nchoosek(A,k);
end

contained inside this cell array:

>> C{:}
ans =
   1
   2
   3
   4
   5
ans =
   1   2
   1   3
   1   4
   1   5
   2   3
   2   4
   2   5
   3   4
   3   5
   4   5
ans =
   1   2   3
   1   2   4
   1   2   5
   1   3   4
   1   3   5
   1   4   5
   2   3   4
   2   3   5
   2   4   5
   3   4   5
ans =
   1   2   3   4
   1   2   3   5
   1   2   4   5
   1   3   4   5
   2   3   4   5
ans =
   1   2   3   4   5

Without padding they will not fit into one numeric array, as they have different number of columns. To pad them try this:

C = cell(size(A));
for k = 1:numel(C)
    tmp = nchoosek(A,k);
    C{k} = [tmp,NaN(size(tmp,1),numel(A)-k)];
end
N = cell2mat(C);

which creates this numeric array:

>> N
N =
     1   NaN   NaN   NaN   NaN
     2   NaN   NaN   NaN   NaN
     3   NaN   NaN   NaN   NaN
     4   NaN   NaN   NaN   NaN
     5   NaN   NaN   NaN   NaN
     1     2   NaN   NaN   NaN
     1     3   NaN   NaN   NaN
     1     4   NaN   NaN   NaN
     1     5   NaN   NaN   NaN
     2     3   NaN   NaN   NaN
     2     4   NaN   NaN   NaN
     2     5   NaN   NaN   NaN
     3     4   NaN   NaN   NaN
     3     5   NaN   NaN   NaN
     4     5   NaN   NaN   NaN
     1     2     3   NaN   NaN
     1     2     4   NaN   NaN
     1     2     5   NaN   NaN
     1     3     4   NaN   NaN
     1     3     5   NaN   NaN
     1     4     5   NaN   NaN
     2     3     4   NaN   NaN
     2     3     5   NaN   NaN
     2     4     5   NaN   NaN
     3     4     5   NaN   NaN
     1     2     3     4   NaN
     1     2     3     5   NaN
     1     2     4     5   NaN
     1     3     4     5   NaN
     2     3     4     5   NaN
     1     2     3     4     5

Best Answer

Related Solutions

MATLAB: Sum of Multiplication of column values in cell array

MATLAB: 1D array combinations

Related Question