Anomaly with the number 32??

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Nathan McCaughey
Nathan McCaughey 2011년 8월 11일
I am using this line to determine if an element of a cell array is empty:
tf = isequal({' '}, Array(row,col));
When
Array(row,col) = 32
tf returns 1, which should actually be 0. Why is this happening?

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Oleg Komarov
Oleg Komarov 2011년 8월 11일
Be careful with cell arrays:
isequal({' '}, 32) % 0
Array = {32};
isequal({' '},Array) % true
It is not comparing what's inside but is asking the following question: "Is a cell equal to a cell?"
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Oleg Komarov
Oleg Komarov 2011년 8월 11일
Ok, I guess I was wrong about the question the isequal is asking.
Then it does ask enquire the content (but I do remember there was a peculiar behaviour, can't find the post).
The point here is that double(' ') == 32, i.e. the empty space is converted to it's corresponding numeric value according to the ASCII table.
Nathan McCaughey
Nathan McCaughey 2011년 8월 11일
I thought something curious was going on. Thanks.

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Arturo Moncada-Torres
Arturo Moncada-Torres 2011년 8월 11일
To know if a cell array is empty, I would recommend you to do the following:
myEmptyCells = cellfun(@isempty,cellArray);
As to this strange conduct, sometimes cell arrays can be tricky. I recommend you to read this great post by Loren regarding them.
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Arturo Moncada-Torres
Arturo Moncada-Torres 2011년 8월 12일
It would work anyway. If you want to use it with _isequal_ you can do something like this:
a{1} = 1;
a{2} = 'hello';
a{3} = '';
a{4} = 45;
b = cell(1,4);
myEmptyCells = cellfun(@isequal, a, b);
Jan
Jan 2011년 8월 13일
BTW, cellfun('isempty') is much faster than cellfun(@isempty)!

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