Brace indexing error maybe complex ?

Hello everyone !

The famous brace indexing. I can't get ride of, i don't see where i do something wrong.

The main structure:

close all;
clearvars;
load Dataset\posture.mat;
signal=datablock1.data;
Fe=1000;
t=0:0.001:10;

%Create excel
Tremor_functions.excel;

%EMG analysis
for mrkr=1:6
    Tremor_functions.Timestamp(markers,mrkr,Fe)
    for muscle=1:4
        Tremor_functions.signal_processing(Debut,Fin,muscle,signal,Fe,mrkr,t);
    end
end
%Fill with data
Tremor_functions.fill_excel(folder,Answer)

First i create an excel and i create some column in it

        function excel
            Prompt={'Surname', 'Name', 'Birthday (xx xx xxxx)','Evaluation (yyyy yy yy)'};
            Dlgtitle='Donnees patient';
            Def={'John','Doe','01 01 1961','2015 02 16'};
            Answer=inputdlg(Prompt,Dlgtitle,1,Def);
            Info_patient={Answer{1},Answer{2},Answer{3}};
            Eval_date={'Evaluation',Answer{4}};
            e= Answer{4};
            assignin('base','Answer',e);
            Muscle={'Fl_Pr','Ex_Su','Bic','Tri'};
            Taches=[1;2;3;4;5;6];
            Taches_c={'Taches'};
            folder = [Answer{1},' ',Answer{2},' ',num2str(Answer{3})];
            assignin('base','folder',folder)
            if ~exist(folder, 'dir')
                mkdir(folder);
            end
            filename = 'Info_patient.xlsx';
            assignin('base','filename',filename)
            fullname = fullfile(folder, filename);
            assignin('base','fullname',fullname)
            xlswrite(fullfile(folder,Answer{4}),Info_patient,'Fpic','A2');
            xlswrite(fullfile(folder,Answer{4}),Eval_date,'Fpic','A3');
            xlswrite(fullfile(folder,Answer{4}),Muscle,'Fpic','B4');
            xlswrite(fullfile(folder,Answer{4}),Taches,'Fpic','A5');
            xlswrite(fullfile(folder,Answer{4}),Taches_c,'Fpic','A4');
        end

At the end of my signal processing i have gathered information that i want to put in my excel sheet, i start with that:

        function fill_excel(folder,Answer)
            xlswrite(fullfile(folder,Answer{4}),Fpic,'Fpic','B5');
        end

But when i run it, i have Brace indexing is not supported for variables of this type.

Error in Tremor_functions.remplir_excel (line 116)

xlswrite(fullfile(folder,Answer{4}),Fpic,'Fpic','B5');

When i don't have something else. I have assigned some of variables, but it doesn't work.

If someone have a clue !

Thanks !

Answer 1

[Stephen23]

"I can't get ride of, i don't see where i do something wrong."

You assign the content of the fourth cell of Answer to variable e (so e is a character vector):

Answer=inputdlg(Prompt,Dlgtitle,1,Def);
...
e= Answer{4}; % e is a char vector

which you then magically make appear in a different workspace with the name Answer (do you see the problem now?)

assignin('base','Answer',e);

which you then try to access as if it was still the same Answer as in the first workspace:

..fill_excel(folder,Answer)

where inside fill_excel you try to access its fourth cell (but of course character vectors do not have cells):

xlswrite(fullfile(folder,Answer{4}),Fpic,'Fpic','B5')
%                        ^^^^^^ character vector    

This is a classic example of obfuscated code that relies on assignin to make data magically jump between workspaces thus causing simple bugs that are then difficult to debug because of that pointless obfuscation. Much better** code would just pass the data reliably as input/output arguments, just as the MATLAB documentation recommends

https://www.mathworks.com/help/matlab/matlab_prog/share-data-between-workspaces.html

** better in the sense simpler, faster, neater, more efficient, clearer, less buggy, and easier to debug.

[John Doe]

Thanks for your detailed answer Stephen, i'll try to make the right adjustment you advised :) !

[Stephen23]

@John Doe: let us know how it goes or if you have any more questions or if anything is unclear.

You can also accept my answer if it resolves your original question.

[John Doe]

Hello Stephen, sorry i was away this week. I'm still trying to fix my problem ^^ but i accept your response of course, i just don't get it yet ^^

[Stephen23]

"i just don't get it yet"

All of the different workspaces, assignin, etc. are just distractions and obfuscations that make it harder to understand the bug. But basically you are doing this:

Answer = {'cat','in','hat'}

Answer = 1x3 cell array
    {'cat'}    {'in'}    {'hat'}

Answer = Answer{2} % oops... same name, but no longer a cell array!

Answer = 'in'

fullfile('whatever',Answer{2}) % not a cell array, so why use curly braces?

Brace indexing is not supported for variables of this type.

[John Doe]

Super i understand much better now, you're a pedagogue champ' Stephen ! Thanks a lot !

I have much more question for u. I'll write those in others topic !