"Warning: Escaped character '\P' is not valid. See 'doc sprintf' for supported special characters." after calling stairs, scatter, histogram functions.

Hello community,

I'm using MATLAB on a Technical Workstation (TWS) running MATLAB R2018b and running the same code (but I keep improving it) on the same machine every day.

>> ver

-----------------------------------------------------------------------------------------------------

MATLAB Version: 9.5.0.944444 (R2018b)

MATLAB License Number: xxxxxx

Operating System: Microsoft Windows 10 Enterprise Version 10.0 (Build 17763)

Java Version: Java 1.8.0_152-b16 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode

-----------------------------------------------------------------------------------------------------

MATLAB Version 9.5 (R2018b)

Simulink Version 9.2 (R2018b)

Curve Fitting Toolbox Version 3.5.8 (R2018b)

MATLAB Coder Version 4.1 (R2018b)

MATLAB Compiler Version 7.0 (R2018b)

MATLAB Compiler SDK Version 6.6 (R2018b)

MATLAB Report Generator Version 5.5 (R2018b)

Simulink Coder Version 9.0 (R2018b)

Statistics and Machine Learning Toolbox Version 11.4 (R2018b)

Vehicle Network Toolbox Version 4.1 (R2018b)

Four days ago I got this "Warning: Escaped character '\P' is not valid. See 'doc sprintf' for supported special characters." after calling some functions such as stairs, scatter, histogram. Here is the output:

>> dtt = [datetime(2021,12,13,12,07,01),datetime(2021,12,13,12,07,05)];

>> stairs(dtt,[2,3])

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

Warning: Error updating Stair.

Error: <a href="matlab: opentoline('C:

>> scatter(dtt,[2,3])

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

Warning: Error updating Scatter.

Error: <a href="matlab: opentoline('C:

However plot function works perfectly fine. Maybe it's because it is a built-in function, or maybe because it is stored in a different folder than that of the other functions. MATLAB toolboxes path is "C:\Program Files\MATLAB\R2018b\toolbox\matlab\..." and I guess the "\P" issue comes from there.

I've already read all the existing threads related to this warning, but I couldn't fix this issue. I can say I tried to install "Fuzzy Logic Toolbox" on Thursday, but I couldn't because I haven't got administartor privilegies on this TWS and from Friday on I keep getting this warning.

What do you suggest me to try?

Thank you all in advance.

Regards,

Simona

[Walter Roberson]

I suggest that you debug by using

dbstop if warning

[Simona Vermiglio]

Hello,

I get

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

Warning from defaulterrorcallback (line 9)

warning(id, msg);

where defaulterrorcallback is the following:

function defaulterrorcallback(~, evt)
% The default value for ErrorCallback properties.

%   Copyright 2009-2017 The MathWorks, Inc.
[id, msg] = matlab.graphics.internal.prepareDefaultErrorCallbackWarning(evt);
stack = dbstack('-completenames');
if (size(stack,1) == 1)
    warningstatus = warning('OFF', 'BACKTRACE');
    warning(id, msg);
    warning(warningstatus);
else
    warning(id, msg);
end

end

I looked into this function the whole yesterday, but at the end I gave up.

I've tried anything I can do. Now I think the only way to recover the full control of MATLAB is to uninstall and reinstall it. :/

[Steven Lord]

Can you set an error breakpoint to stop when a warning is issued and run this code? When MATLAB stops at the warning, show us what this displays:

thestack = dbstack;
for stackframe = 1:numel(thestack)
    fprintf("Frame %d:\n", stackframe)
    disp(thestack(stackframe))
end

[Simona Vermiglio]

Hello Steven,

If I run

dtt = [datetime(2021,12,13,12,07,01),datetime(2021,12,13,12,07,05)];
stairs(dtt,[2,3])

your code displays

Frame 1:

file: 'defaulterrorcallback.m'

name: 'defaulterrorcallback'

line: 9

However my code is much more complex and it involves many scripts, nested functions and scatter, histogram and some other functions as well (saveas).

Thus, I also get some more warnings, such as:

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

Warning from defaulterrorcallback (line 12)

warning(id, msg);

Warning: Error updating Histogram.

Error: <a href="matlab: opentoline('C:

Warning: Error creating or updating Quadrilateral

Error in value of property ColorData

Array is wrong shape or size

Warning: Error creating or updating LineLoop

Error in value of property ColorData

Array is wrong shape or size

Warning: Error creating or updating LineLoop

Error in value of property ColorData

Array is wrong shape or size

Warning from defaulterrorcallback (line 12)

warning(id, msg);

Now, I've just run my code followed by yours.

There are two kinds (maybe) of warnings. The output of your code after the first type of warning is:

Frame 1:

file: 'defaulterrorcallback.m'

name: 'defaulterrorcallback'

line: 12

Frame 2:

file: 'print.m'

name: 'print'

line: 36

Frame 3:

file: 'saveas.m'

name: 'saveas'

line: 181

Frame 4:

file: 'Plot_Sigma.m'

name: 'Plot_Sigma'

line: 97

The output after the second type is

Frame 1:

file: 'defaulterrorcallback.m'

name: 'defaulterrorcallback'

line: 12

Frame 2:

file: 'alternatePrintPath.p'

name: 'alternatePrintPath'

line: 0

Frame 3:

file: 'alternatePrintPath.p'

name: 'alternatePrintPath'

line: 0

Frame 4:

file: 'alternatePrintPath.p'

name: 'alternatePrintPath'

line: 0

Frame 5:

file: 'print.m'

name: 'print'

line: 82

Frame 6:

file: 'saveas.m'

name: 'saveas'

line: 181

Frame 7:

file: 'Plot_Sigma.m'

name: 'Plot_Sigma'

line: 97

I understand the source of the problem might be in the path I pass to the saveas function.

However, I got the same warning also if I just call scatter or stairs function, so I guess the initial warning is raised from there.

Hope I've been clear. Sorry if I've been too long.

Thanks!

[Simona Vermiglio]

And I also get this one:

Frame 1:

file: 'defaulterrorcallback.m'

name: 'defaulterrorcallback'

line: 12

Frame 2:

file: 'mlprintjob.p'

name: 'mlprintjob.setPaintDisabled'

line: 0

Frame 3:

file: 'alternatePrintPath.p'

name: 'alternatePrintPath'

line: 0

Frame 4:

file: 'alternatePrintPath.p'

name: 'alternatePrintPath'

line: 0

Frame 5:

file: 'onCleanup.m'

name: 'onCleanup.delete'

line: 60

Frame 6:

file: 'alternatePrintPath.p'

name: 'alternatePrintPath'

line: 0

Frame 7:

file: 'print.m'

name: 'print'

line: 82

Frame 8:

file: 'saveas.m'

name: 'saveas'

line: 181

Frame 9:

file: 'Plot_Sigma.m'

name: 'Plot_Sigma'

line: 9

[Walter Roberson]

What shows up for

which -all print

[Simona Vermiglio]

C:\Program Files\MATLAB\R2018b\toolbox\matlab\graphics\print.m

print is a Java method % Shadowed com.mathworks.hg.peer.HeavyweightLightweightContainerFactory$FigurePanelContainerLight method

print is a Java method % Shadowed com.mathworks.mwswing.MJPanel method

print is a Java method % Shadowed javax.swing.JPanel method

print is a Java method % Shadowed javax.swing.JComponent method

print is a Java method % Shadowed java.awt.Container method

print is a Java method % Shadowed java.awt.Component method

print is a Java method % Shadowed com.mathworks.mde.array.ArrayEditor method

print is a Java method % Shadowed com.mathworks.mde.desk.PlotableClientBase method

print is a Java method % Shadowed com.mathworks.widgets.desk.DTClientBase method

print is a Java method % Shadowed com.mathworks.hg.util.InfoPanel method

print is a built-in method % Shadowed javahandle.com.mathworks.hg.peer.HeavyweightLightweightContainerFactory$FigureP

I think we're getting to the point...

I can read "shadowed" too many times... :')

[Walter Roberson]

No, "shadowed" is fine for this purpose. It was the first line that I needed for this purpose.

I need to check something...

[Simona Vermiglio]

OK. :)

Actually, I have just tried to move the path of my graphics subfolder to the top in the "Set Path" window, but nothing changed.

[Walter Roberson]

Focusing on this for a moment:

Frame 2:
    file: 'print.m'
    name: 'print'
    line: 36

In your release, line 36 of print.m is drawnow() . So some function called by drawnow() is having a problem.

Notice that the warning message is effectively at every prompt. drawnow() is called internally before each prompt would be given.

What is your current directory at the time of the problem? And what .m or .p files are stored in your current directory?

[Simona Vermiglio]

My current directory is

"E:\MATLAB\..."

and there are several .m and .mat files. No .p files.

I didn't add any new files in the folder of my current directory within the period limited by "the code is working fine" time and "the code is not working anymore" time.

[Walter Roberson]

I would first experiment by changing directory away from the folders that MATLAB is installed in and doing a trial plot there.

Answer 1

[Simona Vermiglio]

Hello,

finally I gave up and decided to install a new MATLAB version.

That fixed the issue.

Thank you all for your help.