error using unique function

s is a cell matrix (178000x9) I want to find the unique values of s in the first column. ID=unique(s(:,1));

I received the following error. Error using cell/unique (line 95) Input A must be a cell array of string

what could be the reason?

[Sean de Wolski]

If the first column is all non-numeric it would not be throwing that error. What is returned from:

iscellstr(s(:,1))

Answer 1

[Mike Hosea]

What type of data is in the cell array? When you use UNIQUE on a cell array, the only case that's supported is when the elements of the cell array are strings. Is that case not working for you?

>> c = {'abc','abc','def','defg'}';
>> unique(c(:,1))
ans = 
    'abc'
    'def'
    'defg'

[Danielle Leblanc]

no . I am receiving an error Error using cell/unique (line 95) Input A must be a cell array of string

[Mike Hosea]

Do you have [] entries? Make sure that any empty entries are '', not [].

[Danielle Leblanc]

how can I tell if I have []. visually I can't because it take too long to load and I have too many observations

[Sean de Wolski]

You can use iscellstr as I did above.

[Danielle Leblanc]

iscellstr(s(:,1))

ans =

     0

[Mike Hosea]

Yes, this is what we expected. You do not have a cell array of only strings. You can find the non-strings with

find(cellfun(@(x)~ischar(x),s))

You do not mention where this data came from. If it began as a

s = cell(m,n);

and was later partially populated, then you might resolve the problem by changing that to

s = repmat({''},m,n);

[Danielle Leblanc]

Thanks this solved the problem

Answer 2

[Wayne King]

Is it a cell array of numeric values?

You can use cell2mat()

A = {1 5 9 ; 2 3 4; 2 4 5};
B = unique(cell2mat(A(:,1)));

[Danielle Leblanc]

column 1 contains names . it is non-numeric