table on workspace isn't recognized as table

Hi,

I have a question that puzzles me.

On my workspace I have a table as such:

name value

left_precentral_betas 25x8 table

and this is how I created it:

left_precentral_betas = table(left_precentral(:,1),left_precentral(:,2),left_precentral(:,3)...
      ,left_precentral(:,4),left_precentral(:,5),left_precentral(:,6),...
      left_precentral(:,7),left_precentral(:,8), 'VariableNames',...
      {'Right Palm Medial', 'Right Back Medial','Left Palm Medial',...
      'Left Back Medial','Right Palm Lateral','Right Back Lateral'...
      ,'Left Palm Lateral','Left Back Lateral'}) ;

yet I can't use writetable function:

writetable(left_precentral_betas,[PATHOUT,'left_motor.txt']);

I get this error:

Error using writetable (line 139)

First argument must be a table.

istable(left_precentral_betas);

gives me 0. If it's not a table, why it's defined as table in my workspace?

If I'm defining the table wrongly, why do I have it as table in my workspace?

and how can I write or save this table/non table as .txt?

Kind regards,

Hatice

[Walter Roberson]

What shows up for

class(left_precentral_betas)

[Hatice Sahin]

ans =

'table'

[Guillaume]

Note that this won't solve your problem at all but a much simpler way to construct your table would be with:

%if size(left_precental, 2) is 6:
left_precentral_betas = array2table(left_precentral, 'VariableNames', {'Right Palm Medial', 'Right Back Medial', 'Left Palm Medial', 'Left Back Medial', 'Right Palm Lateral', 'Right Back Lateral', 'Left Palm Lateral', 'Left Back Lateral'});
%if not
left_precentral_betas = array2table(left_precentral(:, 1:6), 'VariableNames', {'Right Palm Medial', 'Right Back Medial', 'Left Palm Medial', 'Left Back Medial', 'Right Palm Lateral', 'Right Back Lateral', 'Left Palm Lateral', 'Left Back Lateral'});

Now, with regards to your problem, can you issue at the command prompt

dbstop if error

then attempt to write the table. When it errors, it will stop in the debugger inside writetable. At this point, what is

class(T)

Also, what is

which istable -all

[Hatice Sahin]

Hi,

Thank you very much for your tips!

Soo, I assume I should have written class(data) instead of class(T) because I had only data, msg and writeFunctionName left on my workspace. So I did;

K>> class(data)

ans =

    'table'
    
K>> which istable -all
..myfoldernames\spm12\external\fieldtrip\compat\matlablt2013b\istable.m
C:\Program Files\MATLAB\R2019b\toolbox\matlab\datatypes\istable.m                                                          % Shadowed

Looks like the toolbox I used to analyze my data (spm12) somehow interferes with this function. How can I get rid of it?

Kind regards,

Hatice

[Walter Roberson]

You should remove spm12\external\fieldtrip\compat\matlablt2013b from your path . It is intended as compatibility functions for use with versions before R2013b.

[Hatice Sahin]

I removed it from the path and it works perfect now. Thank you very much!

Answer 1

[Guillaume]

"Soo, I assume I should have written class(data)"

No, if you'd followed my instruction, when the error occured matlab should have entered the debugger in the workspace of writable (because of the dbstop if error you issued earlier). Within the workspace of writetable, your original variables don't exist and the table is called T. At least, in R2019b and I assume in previous versions as well.

Anyway, as the which shows, the problem is that the fieldtrip toolbox overrides the built-in istable with its own incompatible version.

From other questions I've seen here, the fieldtrip toolbox has a nasty habit of overriding matlab built-in functions with its own incompatible version. isrow was a particular nasty one I've seen as it prevented proper matlab startup.

[Hatice Sahin]

It works now! Thank you very much for your help.

Answer 2

[Subhadeep Koley]

As far as my knowledge goes MATLAB does not support Blank Space in variable names. It can only contain letters, numbers or underscore. Blank spaces or symbols are not allowed. Therefore it should throw error when you are passing 'Right Palm Medial' as a variable name.

Give the below code a try. I'm not getting any error in my end with the code below.

clc;
% 20-by-20 Random data
left_precentral = rand(20, 20);
% Make the table
left_precentral_betas = table(left_precentral(:, 1), left_precentral(:, 2), left_precentral(:, 3),...
                            left_precentral(:, 4), left_precentral(:, 5), left_precentral(:, 6),...
                            left_precentral(:, 7), left_precentral(:, 8), 'VariableNames',...
                            {'RightPalmMedial', 'RightBackMedial', 'LeftPalmMedial',...
                            'LeftBackMedial', 'RightPalmLateral', 'RightBackLateral',...
                            'LeftPalmLateral', 'LeftBackLateral'});
% Write the table
writetable(left_precentral_betas, [PATHOUT, 'left_motor.txt']);

[Hatice Sahin]

Hi,

Thank you very much for your answer.

I have fixed my code and tried, got the same error. Then I cleared variables and directly copied your working code and tried but unfortunately, I still get the same error that says "the first argument must be a table".

Interesting that it works on yours while the very same code doesn't work on mine. I'm using 2019b btw.

Kind regards,

Hatice

[Walter Roberson]

R2019b and later do support arbitrary character vectors for variable names. (It appears that the limit is still 63 characters per name though.)

[Subhadeep Koley]

@ Walter Roberson I did not knew about this change. Thanks for letting me know :)

[Walter Roberson]

In order to use non-identifiers, you need to use dynamic field name syntax, or else pass the variable name as the second index

T.('Right Palm Media')

Or

T{:, 'Right Palm Media'}

But it is supported for R2019b onwards.

Answer 3

[Daniel M]

The issue is that you likely added the entire Fieldtrip toolbox to your path, which is not recommended. I am currently using Fieldtrip for some analysis, and it does not override the istable function in its default behaviour.

Fieldtrip does not recommend adding the whole toolbox to your path. Just run the function ft_defaults.m and it will do it properly for you.

Try it by doing:

    if isempty(which('ft_preprocessing'))        
        restoredefaultpath
        startup;
        
        ft_dir = path/to/main/fieldtrip/folder;
        run(fullfile(ft_dir,'ft_defaults.m'));
    end

The purpose of the if statement is so that you don't need to alter your path everytime you run your script, since this is a time-expensive process.

See also:

http://www.fieldtriptoolbox.org/faq/should_i_add_fieldtrip_with_all_subdirectories_to_my_matlab_path/