Screen.mexw64 file missing or inaccessible on my MATLAB path

The following code i am trying to run :::::The code is also available on Psychtoolbox tutorial by Peter Scarfe

http://peterscarfe.com/ptbtutorials.html

1st basic totally minimal demo on website

>> % Clear the workspace and the screen

sca;

close all;

clearvars;

% Here we call some default settings for setting up Psychtoolbox

PsychDefaultSetup(2);

% Get the screen numbers. This gives us a number for each of the screens

% attached to our computer.

screens = Screen('Screens');

% To draw we select the maximum of these numbers. So in a situation where we

% have two screens attached to our monitor we will draw to the external

% screen.

screenNumber = max(screens);

% Define black and white (white will be 1 and black 0). This is because

% in general luminace values are defined between 0 and 1 with 255 steps in

% between. All values in Psychtoolbox are defined between 0 and 1

white = WhiteIndex(screenNumber);

black = BlackIndex(screenNumber);

% Do a simply calculation to calculate the luminance value for grey. This

% will be half the luminace values for white

grey = white / 2;

% Open an on screen window using PsychImaging and color it grey.

[window, windowRect] = PsychImaging('OpenWindow', screenNumber, grey);

% Now we have drawn to the screen we wait for a keyboard button press (any

% key) to terminate the demo.

KbStrokeWait;

% Clear the screen.

sca;

The following error and suggestion comes::::

In place of the expected mex file this placeholder file was executed:

Screen

This mex file seems to be missing or inaccessible on your Matlab path or it is dysfunctional:

Screen.mexw64

It is important that the folder which contains the Screen mex file is located *before*

the PsychBasic folder on your Matlab path.

On Matlab V7.4 (R2007a) or later versions, the folder

C:\Users\DELL\AppData\Roaming\MathWorks\MATLAB Add-Ons\Collections\Psychtoolbox-3\Psychtoolbox\PsychBasic\MatlabWindowsFilesR2007a\ must be before the folder

C:\Users\DELL\AppData\Roaming\MathWorks\MATLAB Add-Ons\Collections\Psychtoolbox-3\Psychtoolbox\PsychBasic\

type path to display the current path and check for this condition.

If the order is wrong, simply cd into your Psychtoolbox root folder

C:\Users\DELL\AppData\Roaming\MathWorks\MATLAB Add-Ons\Collections\Psychtoolbox-3\Psychtoolbox\ and then run SetupPsychtoolbox again.

That is the simplest way of fixing such path problems - Or to get more diagnostic output.

Seems Screen.m is in the Matlab path before/above Screen.mexw64 instead of after/below it!

This will cause the mex file to be ignored, leading to this error.

Please run SetupPsychtoolbox again, to rectify this problem, or use Matlabs pathtool

to shuffle things into the right order. This folder:

C:\Users\DELL\AppData\Roaming\MathWorks\MATLAB Add-Ons\Collections\Psychtoolbox-3\Psychtoolbox\PsychBasic\MatlabWindowsFilesR2007a

needs to go above/before this folder:

C:\Users\DELL\AppData\Roaming\MathWorks\MATLAB Add-Ons\Collections\Psychtoolbox-3\Psychtoolbox\PsychBasic

On Microsoft Windows with supported Matlab versions (>= V7.4) it could also be that

the required Visual C++ 2015-2019 runtime libraries are missing on your system.

The Psychtoolbox/PsychContributed/ subfolder contains installer files for them, which

you can execute after quitting Matlab. The name of the file is:

vcredist_x64_2015-2019.exe and maybe also vcredist_x64_2010.exe.

I have tried everything whatever suggested here but still same problem persists. Please help regarding this.

[Wanda Liz Diaz Merced]

Im having the same issue! everything was working properly and then suddently i am getting that error. I have not done any updates it just happened. if the matlab people replied to you, please share the answer as like you i have tried everything posted about it and nothing has worked.

Answer 1

[Jan]

The message explains:

This mex file seems to be missing or inaccessible on your Matlab path or it is dysfunctional: Screen.mexw64

Now it is your turn to clarify: Is the file still there? Is the folder included in Matlab's path? Is it working? Is the folder containing the m-file-dummy found earlier in the path? Is the folder containing Screen.m the current folder, such that the MEX function is shadowed?