Escaped character '\U' is not valid. See 'doc sprintf' for supported special support.

Hi MATLAB users,

I know it's asked elsewhere on this webpage (https://ww2.mathworks.cn/matlabcentral/answers/435377-warning-escaped-character-u-is-not-valid). However, I have no idea how to fix it as I'm a newbie.

Below is the warning message that I got from the code. How can I edit it to a valid expression in MATLAB R2022b on Windows 11?

Many thanks in advance!

Warning: Escaped character '\U' is not valid. See 'doc sprintf' for supported special

Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses.

Error in connector.internal.fevalMatlab

Error in connector.internal.fevalJSON

characters. 
> In ps_LST_lga (line 254)
In cfg_run_cm (line 29)
In cfg_util>local_runcj (line 1717)
In cfg_util (line 972)
In cfg_ui>MenuFileRun_Callback (line 710)
In gui_mainfcn (line 95)
In cfg_ui (line 53) 
Current directory                     C:Warning: Escaped character '\U' is not valid. See 'doc sprintf' for supported special
characters. 
> In ps_LST_lga (line 256)
In cfg_run_cm (line 29)
In cfg_util>local_runcj (line 1717)
In cfg_util (line 972)
In cfg_ui>MenuFileRun_Callback (line 710)
In gui_mainfcn (line 95)
In cfg_ui (line 53) 
Warning: Directory already exists. 
> In ps_LST_lga (line 290)
In cfg_run_cm (line 29)
In cfg_util>local_runcj (line 1717)
In cfg_util (line 972)
In cfg_ui>MenuFileRun_Callback (line 710)
In gui_mainfcn (line 95)
In cfg_ui (line 53) 
Preprocessing of T1.nii                                             641s
Preprocessing of FLAIR.nii                                          145s
Coregister FLAIR to T1                                               91s
Initialize lesions 20-Jan-2023 15:21:31 - Failed  'LST: Lesion segmentation (LGA)'
Out of memory.
In file "C:\MRIapp\toolbox\spm12\toolbox\LST\ps_bwlabeln.m" (???), function "ps_bwlabeln" at line 24.
In file "C:\MRIapp\toolbox\spm12\toolbox\LST\ps_LST_lga.m" (???), function "ps_LST_lga" at line 427.

The following modules did not run:
Failed: LST: Lesion segmentation (LGA)

Answer 1

[Jan]

It is a typical bug under Windows, which does not occur, when the software is tested successfully in Linux:

fprintf(['Current folder: ', cd, '\n'])

The Windows file separators \ are interpreted as escape character for fprintf. Solution:

fprintf('Current folder: %s\n', cd)

Now the path appears as argument of fprintf and is not interpreted.

This concerns sprintf, warning and error message also:

error(['Bad folder: ' cd])   % Wrong output under Windows
error('Bad folder: %s', cd)  % Working

Check line 254 of ps_LST_lga.m .

This is another problem: "Warning: Directory already exists." If you show us the corresponding part of the code, suggesting a solution is much easier.

"Out of memory." is not a warning, but a crash.

[Krystal Xiwing Yau]

Hi Jan,

Thank you for your reply!

I'm afraid I do not understand what you meant by "the corresponding part of the code". It occurred altogether when initializing lesion. I have attached the error file for your reference as well.

>> fprintf('Current folder: %s\n', cd)
Current folder: C:\Users\Krystal\Desktop\LST\194T1

Warning: Escaped character '\U' is not valid. See 'doc sprintf' for supported special
characters. 
> In ps_LST_lga (line 254)
In cfg_run_cm (line 29)
In cfg_util>local_runcj (line 1717)
In cfg_util (line 972)
In cfg_ui>MenuFileRun_Callback (line 710)
In gui_mainfcn (line 95)
In cfg_ui (line 53) 
Current directory                     C:Warning: Escaped character '\U' is not valid. See 'doc sprintf' for supported special
characters. 
> In ps_LST_lga (line 256)
In cfg_run_cm (line 29)
In cfg_util>local_runcj (line 1717)
In cfg_util (line 972)
In cfg_ui>MenuFileRun_Callback (line 710)
In gui_mainfcn (line 95)
In cfg_ui (line 53) 
Warning: Directory already exists. 
> In ps_LST_lga (line 290)
In cfg_run_cm (line 29)
In cfg_util>local_runcj (line 1717)
In cfg_util (line 972)
In cfg_ui>MenuFileRun_Callback (line 710)
In gui_mainfcn (line 95)
In cfg_ui (line 53) 
Preprocessing of T1.nii                                             669s
Preprocessing of FLAIR.nii                                          147s
Coregister FLAIR to T1                                               86s
Initialize lesions 31-Jan-2023 13:25:39 - Failed  'LST: Lesion segmentation (LGA)'
Out of memory.
In file "C:\MRIapp\toolbox\spm12\toolbox\LST\ps_bwlabeln.m" (???), function "ps_bwlabeln" at line 24.
In file "C:\MRIapp\toolbox\spm12\toolbox\LST\ps_LST_lga.m" (???), function "ps_LST_lga" at line 427.

The following modules did not run:
Failed: LST: Lesion segmentation (LGA)

[Walter Roberson]

https://github.com/eebrown/LST/blob/origin/master/ps_LST_lga.m line 254 contains

        fprintf([strout, repmat(' ', 1, 72 - numel(strout) - numel(cd_tmp)), cd_tmp, '\n'])

That code has a bug and needs to be changed to

       fprintf( '%s\n', [strout, repmat(' ', 1, 72 - numel(strout) - numel(cd_tmp)), cd_tmp])

[Krystal Xiwing Yau]

Hi Walter Roberson,

I see!

The code for line 290 contains "mkdir(tmpFolder)". The following is the code for your reference:

       % Create temporary folder
        % ID
        id = [num2str(round(rand(1, 1) * 1e4)), '_', num2str(round(rand(1, 1) * 1e4)), '_', num2str(round(rand(1, 1) * 1e4))];        
        tmpFolder = ['LST_tmp_', id];
        mkdir(tmpFolder)

        % Preprocessing for T1

Thank you.

[Walter Roberson]

@Krystal Xiwing Yau

Yes, it does, but I do not know why you are pointing that out to me ?