uigetfile Multiselect option not working for single file select

I have been trying to figure out why you can't select a single file, if you have the 'MultiSelect' option set to 'on' in the uigetfile command. I need to be able to select 'one or more' files. Here is the code:

% Select and Open file
[files, pathname] = uigetfile({'*.xls*'; '*.csv'}, ...
    'Select One or More Files', 'MultiSelect', 'on');  
for filecount = 1:length(files)
    filename = convertCharsToStrings(files(filecount));
    opts = detectImportOptions(filename, VariableNamingRule="modify");
    MDRdata = readtable(filename, opts);
    time = datetime(MDRdata.ZuluDate_Time,"InputFormat",'yyyy-MM-dd''T''HH:mm:ss.SSS''Z');
    time.Format = 'HH:mm:ss.SSS';

....

I keep getting the following:

"Error using detectImportOptions

Unable to find or open '1'. Check the path and filename or file permissions.

Error in ApacheMDRProgram_04162024 (line 12)

opts = detectImportOptions(filename, VariableNamingRule="modify");"

It works fine if you select more than one file.

[Michael Shane]

If the answer is this configuration only lets you select multiple files then that is fine. I would just have to have two different scripts. One for a single file, one for multiple.

[Stephen23]

"I would just have to have two different scripts. One for a single file, one for multiple.2

Not required. Just use CELLSTR.

Answer 1

[Voss]

You don't need separate scipts/functions.

Since files is a cell array when multiple files were selected, and files is a character vector when one file was selected, simply make files a cell array (the more general case) if it's not already:

if ~iscell(files)
    files = {files};
end

Or, more succinctly, without explicitly checking the class yourself:

files = cellstr(files);

By the way, you don't need convertCharsToStrings (or to convert to strings at all). You can index files using curly braces {} to get the character vector representing the file name.

% Select and Open file(s)
[files, pathname] = uigetfile({'*.xls*'; '*.csv'}, ...
    'Select One or More Files', 'MultiSelect', 'on');

% user hit cancel -> do nothing
if isequal(files,0)
    return
end

% make sure files is a cell array
if ~iscell(files)
    files = {files};
end

% loop over the selected files
for filecount = 1:length(files)
    filename = files{filecount};
    % ...
end

[Michael Shane]

Wow, that worked perfectly. I didn't even think about there being a difference in the variable types. I really appreciate it.

[Voss]

You're welcome!

Answer 2

[Walter Roberson]

[files, pathname] = uigetfile({'*.xls*'; '*.csv'}, ...
    'Select One or More Files', 'MultiSelect', 'on');  
if isnumeric(files)
    return;   %user canceled
end
files = cellstr(files);

if files was returned as a cell array because the user selected multiple files, then cellstr() returns the cell unchanged.

If files was returned as a character vector because the user selected one file, then cellstr() wraps the character vector in a cell.

Afterwards, the result will be a cell array (that might possibly have only one entry)

Answer 3

[Dallas Perkins]

Hi Michael,

If you only select one file uigetfile will return a char array instead of a cell array of char arrays. The line calling convertCharsToStrings in that scenario will take the first char of the filename and convert it to a string instead of the full filename. This errors later since it's not a valid filename. It looks like you need to add some additional logic to detect if you are returning a single or multiple files.