Screen keeps freezing and not responding

Programming Help
1

I am using MATLAB 2020 on Mac OS and everytime I run this code, they screen turns grey followed by an error sound, however, no error message is displayed in the command window.

% Clear the workspace
close all;
clearvars;
sca;

% Setup PTB with some default values
PsychDefaultSetup(2);

% Seed the random number generator. Here we use the an older way to be
% compatible with older systems. Newer syntax would be rng('shuffle'). Look
% at the help function of rand "help rand" for more information
rand('seed', sum(100 * clock));

% Set the screen number to the external secondary monitor if there is one
% connected
screenNumber = max(Screen('Screens'));

% Define white, grey and black
white = WhiteIndex(screenNumber);
grey = white / 2;
black = BlackIndex(screenNumber);

% Open an on screen window
[window, windowRect] = PsychImaging('OpenWindow', screenNumber, grey);

% Get the size of the on screen window
[screenXpixels, screenYpixels] = Screen('WindowSize', window);

% Query the frame duration
ifi = Screen('GetFlipInterval', window);

% Set up alpha-blending for smooth (anti-aliased) lines
Screen('BlendFunction', window, 'GL_SRC_ALPHA', 'GL_ONE_MINUS_SRC_ALPHA');

% Setup the text type for the window
Screen('TextFont', window, 'Ariel');
Screen('TextSize', window, 36);

% Get the centre coordinate of the window
[xCenter, yCenter] = RectCenter(windowRect);


%----------------------------------------------------------------------
%                       Keyboard information
%----------------------------------------------------------------------

% Define the keyboard keys that are listened for. We will be using the left
% and right arrow keys as response keys for the task and the escape key as
% a exit/reset key
escapeKey = KbName('ESCAPE');
leftKey = KbName('LeftArrow');
rightKey = KbName('RightArrow');
downKey = KbName('DownArrow');

%----------------------------------------------------------------------
%                       Fixation cross
%----------------------------------------------------------------------

% Here we set the size of the arms of our fixation cross
fixCrossDimPix = 10;

% Now we set the coordinates (these are all relative to zero we will let
% the drawing routine center the cross in the center of our monitor for us)
xCoords = [-fixCrossDimPix fixCrossDimPix 0 0];
yCoords = [0 0 -fixCrossDimPix fixCrossDimPix];
allCoords = [xCoords; yCoords];

% Set the line width for our fixation cross
lineWidthPix = 4;

%----------------------------------------------------------------------
%                            Colors
%----------------------------------------------------------------------

% We are going to use three colors for this demo. Red, Green and blue.
wordList = {'Green', 'Magenta', 'Orange'};
Colors = [0 1 0; 1 0 1; 0.8500 0.3250 0.0980];

%----------------------------------------------------------------------
%                  Define positions of sequences
%----------------------------------------------------------------------

leftX = screenXpixels/2.5;
leftY = screenXpixels/1.6;
rightX = screenXpixels/1.7;
rightY = screenYpixels/1.6;
upX = screenXpixels/2.1;
upY = screenYpixels/2.6;

left = [leftX leftY];
right = [rightX rightY];
up = [upX upY];

%----------------------------------------------------------------------
%                  Randomise temporal order of trials
%----------------------------------------------------------------------
 
trialorder = [1 0 0 0 0];
randtemp = shuffle(trialorder);

%----------------------------------------------------------------------
%                           Trial loop
%----------------------------------------------------------------------
nTrials = 5;

for trial = 1:randtemp
    
    % randomise position of sequences
    randpos = shuffle(left, right, up);
    
    % fixation cross
    % Draw the fixation cross in white, set it to the center of our screen and
    % set good quality antialiasing
    Screen('DrawLines', window, allCoords,...
    lineWidthPix, white, [xCenter yCenter], 2);

    % Derive distributions
    seq1 = distribution(0.02, 0.126, 0.146, 0.106, 5); % high variance
    seq2 = distribution(0.02, 0.126, 0.146, 0.106, 5); % low variance
    seq3 = distribution(0.02, 0.126, 0.146, 0.106, 5); % low variance
    
    seq4 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    seq5 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    seq6 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    
    seq7 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    seq8 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    seq9 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    
    seq10 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    seq11 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    seq12 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    
    seq13 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    seq14 = distribution(0.02, 0.126, 0.146, 0.106, 5);
    seq15 = distribution(0.02, 0.126, 0.146, 0.106, 5);

    if trial == 1 
       DrawFormattedText(window, 'Name the color \n\n Press Any Key To Begin',...
       'center', 'center', black);
       Screen('Flip', window);
       KbStrokeWait;
    end
    
    if randtemp() == 0
        % trail 1
        Screen('DrawText', num2str(seq1), white, randpos(1));
        Screen('DrawText', num2str(seq2), white, randpos(2));
        Screen('DrawText', num2str(seq3), white, randpos(3));
        WaitSecs(0.75)
        Screen('Flip', window);
        KbStrokeWait;
           
        Screen('DrawText', num2str(seq2), white, randpos(1));
        Screen('DrawText', num2str(seq3), white, randpos(2));
        WaitSecs(0.75)
        Screen('Flip', window);
        KbStrokeWait;
        
        %trial 2
        %repeat
        
    else 
        Screen('DrawText', num2str(seq13), white, randpos(1));
        Screen('DrawText', num2str(seq14), white, randpos(2));
        Screen('DrawText', num2str(seq15), white, randpos(3));
        WaitSecs(0.75)
        Screen('Flip', window);
        KbStrokeWait;
           
        Screen('DrawText', num2str(seq13), white, randpos(1));
        Screen('DrawText', num2str(seq14), white, randpos(2));
        WaitSecs(0.75)
        Screen('Flip', window);
        KbStrokeWait;
    end
end       

        

      

% Flip to the screen
Screen('Flip', window);

% Wait for a key press
KbStrokeWait;

% Clear the screen
sca;
2

wrap your code in a block like this:
try

catch me
sca
rethrow(me)
end

then, you can see what the error is. If not, reduce the code to the bare minimum to reproduce your problem

3

Thanks! I used this and it showed that the error was to do with writing ‘Shuffle’ instead of ‘shuffle’. Now, although the screen doesn’t freeze and allows me to escape when I press any key, it just shows a grey screen, with none of the rest of the code running - I’m not sure why

4

[for trial = 1:randtemp] seems like error is occurring here. Randtemp is not useful as a counter for the for loop. Try numel(randtemp) instead.