How to convert cell to cell array of character vectors.

Hi,

So I have a basic table that looks like this but has over 60 000 rows:

A = [48.44, 48.16].';
B = ['A', 'B'].';
C = table(A, B);

The problem is that when I type unique(C.B) Matlab complains : Cell array input must be a cell array of character vectors.cell array of character vectors.

The commands class(btl_data.POLYGON) returns 'cell', and iscellstr(btl_data.POLYGON) returns 0. The commands char(C.B) and cellstr(C.B) fail (Element 1 is not a string scalar or character array. All elements of cell input must be string scalars or character arrays.)

So I dont know. I know this is really basic but nothing works. Column B really should be only characters.

Thoughts ?

[Srivardhan Gadila]

I see that there is no error with unique(C.B). Can you mention the exact steps followed which is causing the error "Cell array input must be a cell array of character vectors.cell array of character vectors."

[Guillaume]

Note that with your example, B is not a cell array. It's a 2x1 char vector, and unique would work fine with that.

Proper demo data:

A = [48.44, 48.16].';
B = {'A', 'BB'}.';  %with vectors of varying size you would not have been able to create a char matrix
C = table(A, B);

clearly, if iscellstr returns false, then as Adam explains, there's a non char vector in your cell array (maybe [] instead ''?). As the error message tells you, it's at least the first element that is a problem.

[Stephen23]

Note that this line

B = ['A', 'B'].';

is unlikely to be useful. Square brackets are a concatenation operator, so this

['A', 'B']

is exactly equivalent to this:

'AB'

https://www.mathworks.com/help/matlab/matlab_prog/matlab-operators-and-special-characters.html

Answer 1

[Adam Danz]

At least one of the elements in btl_data.POLYGON is not a character vector. This demo below recreates the error.

A = [48.44, 48.16, 50].';
B = ['A', 'B', {5:10}].';
C = table(A, B);

unique(C.B)
% Error using cell/unique (line 85)
% Cell array input must be a cell array of character vectors. 

To find the row numbers of table C that do not contain a char vector in column "B",

notChar_rowIndex = find(~cellfun(@ischar,C.B))
% ans =
%     3

Now you can look at those rows,

C(notChar_rowIndex,:)

[Guillaume]

The error message says it's the first element that's problematic. There may be more so there's indeed value in getting these row indices.

Answer 2

[Blue]

Thank you all for your input.