How to run a for loop multiple times on some images?

Hello,

I am very new to Matlab. I am trying to create a loop to read four images in a file. However, I cannot repeat the for a loop several times. I need to present these 4 images 32 times randomly (each image 8 times). I appreciate it if you help me. This is the code I am already using:

nTrials = 4

for i = 1:nTrials

trial{i} = imread(['A' num2str(i) '.jpg']);

end

fixation = imread('fixation.jpg');

Screen('Preference', 'VisualDebugLevel', 1);

window = Screen('OpenWindow', 0, [100 100 100])

for i = 1:nTrials

texture = Screen('MakeTexture', window, fixation);

Screen('DrawTexture', window, texture);

Screen('Flip', window);

WaitSecs(0.5)

texture = Screen('MakeTexture', window, trial{i});

Screen('DrawTexture', window, texture);

Screen('Flip', window);

WaitSecs(1.5)

end

sca;

nTrials is equal to 4 (since i have just 4 images) but when i change it to more than 4 i receive this error:

imread: unable to find file 'A5.jpg'

Answer 1

[KSSV]

n = repmat(1:4,1,8) ;
idx = randsample(length(n),length(n)) ;
n = n(idx) ;

Run a loop on n, 1:4 stand for the four images respectovely.

[Pouyan]

n = repmat(1:4,1,8) ;

idx = randsample(length(n),length(n)) ;

n = n(idx);

for n = 1:n

trial{n} = imread(['A' num2str(n) '.jpg']);

end

fixation = imread('fixation.jpg');

Screen('Preference', 'VisualDebugLevel', 1);

window = Screen('OpenWindow', 0, [100 100 100])

for n = 1:n

texture = Screen('MakeTexture', window, fixation);

Screen('DrawTexture', window, texture);

Screen('Flip', window);

WaitSecs(0.5)

texture = Screen('MakeTexture', window, trial{n});

Screen('DrawTexture', window, texture);

Screen('Flip', window);

WaitSecs(1.5)

end

sca;

Thanks for your answer but this code just shows two images so does not work.

Answer 2

[Image Analyst]

That file does not exist. Get a list of files that actually exist with dir():

% Get list of files that are in the folder.
fileList = dir('A*.jpg')
if isempty(fileList)
    warningMessage = sprintf('Folder has no JPG images');
    uiwait(errordlg(warningMessage));
    return;
end
% Get all filenames in a list
allFileNames = {fileList.name};
nTrials = length(allFileNames)
% Read in all the images and display them.
for k = 1:nTrials
    trial{k} = imread(allFileNames{k}); 
    imshow(trial{k});
    drawnow;
end

[Pouyan]

Hi

% Get list of files that are in the folder.

fileList = dir('A*.jpg')

if isempty(fileList)

warningMessage = sprintf('Folder has no JPG images');

uiwait(errordlg(warningMessage));

return;

end

% Get all filenames in a list

allFileNames = {fileList.name};

nTrials = length(allFileNames)

% Read in all the images and display them.

for k = 1:nTrials

trial{k} = imread(allFileNames{k});

imshow(trial{k});

drawnow;

end

fixation = imread('fixation.jpg');

Screen('Preference', 'VisualDebugLevel', 1);

window = Screen('OpenWindow', 0, [100 100 100])

for k = 1:nTrials

texture = Screen('MakeTexture', window, fixation);

Screen('DrawTexture', window, texture);

Screen('Flip', window);

WaitSecs(0.5)

texture = Screen('MakeTexture', window, trial{k});

Screen('DrawTexture', window, texture);

Screen('Flip', window);

WaitSecs(1.5)

end

sca;

This code does not make any changes compared to the first code. That is, just shows 4 images which are in the folder. as it has mentioned i want to show this 4 images randomly for 32 times.

Thank you in advance.