How to import files from an outside folder?

I am stuck with the following. I am designing a GUI, which should access files from a different folder as the one where the GUI is located, that is the main matlab folder.

The GUI works fine when I place the files on the main folder, but fails when taking the files from outside folder. The data files are '.txt'. I made an import function that reads the files and separates the column values, as time and data. Only one time array is needed.

This is what I am trying:

    folder = uigetdir('C:\Users\..\data folder');
    files = dir(fullfile(folder, '*.txt')); 
    NF = length(files) ;

for i = 1:length(files)

        A = import_AB_function(files(i).name) ; 
        data{i} = A;
        Ampl_S {i} = (data{:, i}(:,end));

end

    time = data{1, 1}(:,1);
    Amplitudes_all =  cell2mat(Ampl_S);

I can tell that import function is not able to interpret outside files from the main folder, but I can not see the way around it.

Any help please?

Thanks guys

%################################# Error output:

Error using textscan Invalid file identifier. Use fopen to generate a valid file identifier.

Error in import_AB_function (line 36) dataArray = textscan(fileID, formatSpec, endRow(1)-startRow(1)+1, 'Delimiter', delimiter, 'TextType', 'string', 'EmptyValue', NaN, 'HeaderLines', startRow(1)-1, 'ReturnOnError', false, 'EndOfLine', '\r\n');

Error in please (line 22) A = import_AB_function(files(i).name) ;

Answer 1

[Fangjun Jiang]

A = import_AB_function(fullfile(folder,files(i).name))