MATLAB: , oh why does isempty return 0? Questions related to dataset access and return from strfind.

datasetisemptystrfind

Hello all,
I have a dataset array for example called measurement which contains a subfield called tempSequence containing single digits stored as strings (eg. '1', '2', etc.) I want to perform a check for the contents of this field and am using a combination of isempty and strfind and can't seem to get a TRUE return.
Specifically, I want to check that the field contains both a '1' and a '5' like so:
    if(  ~isempty(strfind(measurement.TempSequence, '1')) && isempty(strfind(messung.TempSequence, '5')) )
        % Both 1 and 5 are present, perform operation on different subfield.
    end
If tempSequence is as follows:
K>> measurement.TempSequence
ans = 
      '3'
      '4'
      '5'
      '2'
And strfind returns:
K>> strfind(measurement.TempSequence, '1')
ans = 
      []
      []
      []
      []
Why why why:
K>> isempty(strfind(measurement.TempSequence, '1'))
ans =
       0
Is it something to do with it being a dataset and therefore has attached metadata? Am I using strfind in a dumb way? What am I missing?
Why:
K>> isempty(strfind(measurement.TempSequence, 'foobar'))
ans =
       0
Thank you for reading! Marshall

Best Answer

The output of strfind is a cell array. To be considered empty, a cell array must have no cells whatsoever,
    >> isempty({})
    ans =
         1
This is different from a cell array containing cells with empty matrices
    >> c={[]};
    >> isempty(c)
    ans =
         0
    >> isempty(c{1})
    ans =
         1
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