Question

We have p.e. i = 1:25 iterations.
Each iteration result is a 1xlength(N) cell array, where 0<=N<=25.

iteration 1: 4     5     9    10     20     
iteration 2: 3     8     9    13     14      6
...
iteration 25:  1     2    3

We evaluate the results of all iterations to one matrix sorted according to frequency each value is repeated in descending order like this example:

Matrix=
  Columns 1 through 13
    16    22    19    25     2     5     8    14    17    21     3    12    13
     6     5     4     4     3     3     3     3     3     3     2     2     2
  Columns 14 through 23
    18    20     1     6     7     9    10    11    15    23
     2     2     1     1     1     1     1     1     1     1

Result explanation: Column 1: N == 16 is present in 6 iterations, column 2: N == 22 is present in 5 iterations etc.
If a number N isn’t displayed (in that paradigm N == 4, N == 24) in any iteration, is not listed with frequency index of zero either.

I want to associate each iteration (i) to the first N it is displayed p.e. N == 9 to be present only in first iteration i = 1 and not in i = 2 too, N == 3 only to i = 2 and not in i = 25 too etc until all i‘s to be unique associated to N‘s.

Thank you in advance.

Answer 1

Here’s a way that uses a feature of unique (i.e. that it returns the index to the first value) that was introduced in R2012a

%# make some sample data
iteration{1} = [1 2 4 6];
iteration{2} = [1 3 6];
iteration{3} = [1 2 3 4 5 6];
nIter= length(iteration);

%# create an index vector so we can associate N's with iterations
nn = cellfun(@numel,iteration);
idx = zeros(1,sum(nn));
idx([1,cumsum(nn(1:end-1))+1]) = 1;
idx = cumsum(idx); %# has 4 ones, 3 twos, 6 threes

%# create a vector of the same length as idx with all the N's
nVec = cat(2,iteration{:});

%# run `unique` on the vector to identify the first occurrence of each N
[~,firstIdx] = unique(nVec,'first');

%# create a "cleanIteration" array, where each N only appears once
cleanIter = accumarray(idx(firstIdx)',firstIdx',[nIter,1],@(x){sort(nVec(x))},{});

cleanIter = 
    [1x4 double]
    [         3]
    [         5]

>> cleanIter{1}
ans =
     1     2     4     6