Matlab Newbie here / I want to multiselect files but it always gives me an error

Here is my Code,if i multiselect them files it gives me this error,pls help

Error using fopen
First input must be a file name or a file identifier.

Error in m_Hommel_Rauheitsdaten_Auswertung_Einzelplot (line 18)
fid = fopen(filename,'r');

% Laden der Messdaten
[filename,filepath]=uigetfile({'*.prf','Result file (*.txt)'},'MultiSelect','On'); %Dateiauswahl ?ffnen und zugelassene Dateien festlegen
if isequal (filename,0) % Abbruch wenn keine Datei ausgew?hlt
    disp('No file chosen, program is canceled.');
    return;
end
 v=(0:90:270)
Winkelposition=v;
Zeitpunkt=' Vorher ';
Lagernummer='Huelse';

Plotname=[Lagernummer Zeitpunkt Winkelposition];


%% Cell trfomation

fid = fopen(filename,'r');
i = 1;
tline = fgetl(fid);
C{i} = tline;
while ischar(tline)
    i = i+1;
    tline = fgetl(fid);
    C{i} = tline;
end
fclose(fid);


components = strsplit(C{4},' ');
myValue = components(5);
M=str2double(myValue);

skal=strsplit(C{7},' ');
myValeu= skal(3);
G=str2double(myValeu);



%% 
Newfile=comma2point([filepath '' filename]);


opts = detectImportOptions(Newfile,'FileType','text');

Rauheitsdaten=readmatrix(Newfile,opts);


% Newfile=comma2point([filepath '' filename]);
% Rauheitsdaten=dlmread(Newfile,'\t',2,0);
% X=Rauheitsdaten(:,1);

Answer 1

[Ameer Hamza]

When MultiSelect is on, then uigetfile() returns a cell array. So you need to specify which file to open in fopen like this

fid = fopen(filename{1},'r'); % open first file
i = 1;
tline = fgetl(fid);
C{i} = tline;
while ischar(tline)
    i = i+1;
    tline = fgetl(fid);
    C{i} = tline;
end
fclose(fid);

Or write a for-loop to open all files one by one and read them.

[Firas Guechchati]

thank you for this answer,but

it tells me Brace indexing is not supported for variables of this type.

[Ameer Hamza]

Yes, uigetfile seems to have strange behavior. If you select multiple files, it return a cell array, but if select return a single file, it returns a plain char array. You will need to use an if-block to take care of this condition

if iscell(filename)
    fid = fopen(filename{1},'r');
else
    fid = fopen(filename,'r');
end

Answer 2

[Image Analyst]

Just make sure you include the folder because the user did not necessarily pick files in the current folder:

[filename, folder] = uigetfile({'*.*','Result file (*.txt)'},'MultiSelect','On'); %Dateiauswahl ?ffnen und zugelassene Dateien festlegen
if iscell(filename)
	numFiles = length(filename);
else
	if filename == 0 % User clicked cancel.
		return;
	end
        % If we get here, the user clicked a single file.
	numFiles = 1;
end
for k = 1 : numFiles
	if iscell(filename)
		fullFileName = fullfile(folder, filename{k});
	else
		fullFileName = fullfile(folder, filename);
	end
	fprintf('Opening %s...\n', fullFileName);
% 	fid = fopen(fullFileName,'r');
	% etc.
end