Anomaly with the number 32??

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?

Answer 1

[Oleg Komarov]

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?"

[Nathan McCaughey]

Can you then explain this?

array = {33};

is equal({' '},array) % 0

[Oleg Komarov]

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]

I thought something curious was going on. Thanks.

Answer 2

[Arturo Moncada-Torres]

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.

[Nathan McCaughey]

Thank you Arturo. I have read that post (many times actually).

I am importing an array from excel that contains all different data types. If the excel cell is empty, the cell in the raw matlab array is ' '. Suppose for example my array is:

A =

[1] 'hello' ' ' [45]

and I want to see if A(1,3) is empty (or equal to ' '). Can you adapt your previous sugesstion to accomodate?

[Arturo Moncada-Torres]

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]

BTW, cellfun('isempty') is much faster than cellfun(@isempty)!