Dot indexing is not supported for variables of this type

Hi,

I am developping an app, where i want to load data from a .m fille to fill items for a drop down list. How ever in run into an error "Dot indexing is not supported for variables of this type". Any one knows how to fix this issue ? my code is bellow . Thank you

function startupFcn(app, varargin)
            evalin('base', 'clear all')   
            evalin('base', 'clc') 
            
        
            list = fopen('VehicleList.m','r'); % Read data from the file
            A = textscan(list, '%c');          % Importing data
            fclose(list);                      % close file 
            AB = char(A);                      % Cell to char conversion
            assignin('base','A', A);           % send to workspace
            assignin('base','AB', AB);         % send to workspace
            app.VehicleModelDropDown.Items = AB.VehicleList; % << I get the error here
        
        
        function UpdateVehicleList(app,new_car)
            VehicleList = [app.VehicleModelDropDown.Items new_car];
            save('VehicleList.m','VehicleList','-append');
            app.VehicleModelDropDown.Items = VehicleList;
        end
        end

[Stephen Cobeldick]

AB has type char. What do you expect

AB.VehicleList

to do with a character type variable?

Why are you opening an M-file for reading?:

list = fopen('VehicleList.m','r');

(As opposed to running or calling it). That textscan useage is very ... unusual.

Why do you need evalin everywhere?

[Mohammad Sami]

I suggested to save the file as .mat file. Not as.m. you can use the save and load functions with .mat file.

[Khalala Mamouri]

Ok; lets do it with load same code as before:

• what do i expect for type char ? >> I am not sure i understand you question ... Anyways, i want to set a list of items (Name of vehicules) and i want then to be loaded to the drop down list.

• Why are you opening an M-file for reading?: >> Ok let's use an .mat file then and lets get rid of the textscan thing

list = load('VehicleList.mat','-ascii');
            assignin('base','list', list);
            app.VehicleModelDropDown.Items = list.VehicleList;
        
        
        function UpdateVehicleList(app,new_car)
            VehicleList = [app.VehicleModelDropDown.Items new_car];
            save('VehicleList.mat','VehicleList','-append');
            app.VehicleModelDropDown.Items = VehicleList;
        end
        
        

here is the error i get now :

Error using load
Unknown text on line number 1 of ASCII file VehicleList.mat
"Nissan leaf".

any potential answers to that ?

[Mohammad Sami]

If you want to read and load from plain text file use readmatrix and writematrix functions.

writematrix(VehicleList,'test.txt');
VehicleList  = readmatrix('test.txt','OutputType','string');

[Stephen Cobeldick]

Using load with the -ascii option requires that the file contains only one numeric matrix, as the load documentation clearly states: "ASCII files must contain a rectangular table of numbers, with an equal number of elements in each row."

Your file apparently contains other non-number characters, e.g. the text 'Nissan leaf'.

It seems likely that your file is actually some kind of text file which misleadingly has the extension .mat. But this is just a guess based on the few small clues you have given us so far. If you want any further help then please upload a sample file by clicking the paperclip button, so that someone can help you to import your file data correctly (e.g. using readtable).

[Mohammad Sami]

        function startupFcn(app, varargin)
            VehicleList  = readmatrix('vehiclelist.txt','OutputType','string');
            app.VehicleModelDropDown.Items = VehicleList;
        end
        
        
        function UpdateVehicleList(app,new_car)
            VehicleList = [app.VehicleModelDropDown.Items string(new_car)];
            writematrix(VehicleList,'vehiclelist.txt');
            app.VehicleModelDropDown.Items = VehicleList;
        end

[Khalala Mamouri]

Unfortunately matlab does not allow me to upload the file since it is an app file.

Anyways, yes you where right ! i saved the .mat file in the wrong way and matlab does show me that it is an .map file but in reality it is .m file .

So this is the Updated code with a screen shot , that may help you to debug better the problem. Now load works just fine and loads the data perfectly, however Now i get this error : Reference to non-existent field 'VehicleList'.

It is because matlab can't find the name VehicleList i guess?

  function startupFcn(app, varargin)
            evalin('base', 'clear all')   
            evalin('base', 'clc') 
            
        
            list = load('VehicleList.mat');
            assignin('base','list', list);
            app.VehicleModelDropDown.Items = list.VehicleList; % Reference to non-existent field 'VehicleList'.
        
        
        function UpdateVehicleList(app,new_car)
            VehicleList = [app.VehicleModelDropDown.Items new_car];
            save('VehicleList.mat','VehicleList','-append');
            app.VehicleModelDropDown.Items = VehicleList;
        end

[Mohammad Sami]

Can you check that you have a variable named "VehicleList" in the ".mat" file.

[Khalala Mamouri]

@mohammed your answer is correct !! works just fine with your last code ! thank you so much

[Khalala Mamouri]

          VehicleList  = readmatrix('vehicleList.txt','OutputType','string');
            app.VehicleModelDropDown.Items = VehicleList;
        
        
        
        function UpdateVehicleList(app,new_car)
            VehicleList = [app.VehicleModelDropDown.Items string(new_car)];
            writematrix(VehicleList,'vehicleList.txt');
            app.VehicleModelDropDown.Items = VehicleList;
        end     
        
        

This is my last question i promess haha !

Actualy when i putt more than one car type this error appears :

Error using matlab.ui.control.internal.model.AbstractStateComponent/set.Items (line 184)

Expected input to be a vector.

any solutions please .?

[Mohammad Sami]

Can you amend this part, Also check the txt file has one item per row.

        function UpdateVehicleList(app,new_car)
            VehicleList = [string(app.VehicleModelDropDown.Items) string(new_car)]';
            writematrix(VehicleList,'vehiclelist.txt');
            app.VehicleModelDropDown.Items = VehicleList;
        end

[Mohammad Sami]

Another option can be to use readcell and writecell functions.

        function startupFcn(app, varargin)
            VehicleList  = readcell('vehiclelist.txt');
            app.VehicleModelDropDown.Items = VehicleList;
        end
        
        
        function UpdateVehicleList(app,new_car)
            VehicleList = [cellstr(app.VehicleModelDropDown.Items) cellstr(new_car)]';
            writecell(VehicleList,'vehiclelist.txt');
            app.VehicleModelDropDown.Items = VehicleList;
        end

[Khalala Mamouri]

it works just fine . Wow you are amazing man !