Presenting random images from a file, where each image is presented only once?

Hi,

This is my fourth day of coding ever so bear with me.

Right now I have a folder with images. I want to present each image from the folder randomly once and only once for a certain number of trials.

So far my code looks like this. It successfully presents a random image from the folder, but it can use the same images over again which I don't want.

How do I make it so that each image in the folder is displayed once and only once?

Thank you in advance for your help!

emotionalImageDirectory = 'C:\PsychExperiment\Emotional';
imageTwoVarOne = dir([emotionalImageDirectory '\*.jpg']);
imageTwoVarTwo = numel(imageTwoVarOne);
idx = randi(imageTwoVarTwo);
loadimageTwo = imread(imageTwoVarOne(idx).name);

Answer 1

[Jeff Miller]

Store a random sequence of the images in advance and then cycle through them one by one. Something like this,

emotionalImageDirectory = 'C:\PsychExperiment\Emotional';
imageTwoVarOne = dir([emotionalImageDirectory '\*.jpg']);
imageTwoVarTwo = numel(imageTwoVarOne);
imageseq = randperm(imageTwoVarTwo);
for i=1:imageTwoVarTwo  % or the number of trials you want, which may be less than the n of images
    idx = imageseq(i);
    loadimageTwo = imread(imageTwoVarOne(idx).name);
end

[Robert Newman]

Thank you! What if I wanted to present two images at the same time? Let's say I had another subfolder with non-emotional images, and I wanted them to also be presented once and only once and in a random order. I've tried using a nestled for loop with the break function, but so far this hasn't worked. i.e. something like

emotionalImageDirectory = 'C:\PsychExperiment\Emotional';
imageTwoVarOne = dir([emotionalImageDirectory '\*.jpg']);
shuffleImagesTwo = randperm(numel(imageTwoVarOne));  

for b =1:shuffleImagesTwo
      loadimageTwo = imread(imageTwoVarOne(b).name);
      break
        end   

[Jeff Miller]

Not sure that I follow, but maybe you want two random sequence holders, something like this:

emotionalImageDirectory = 'C:\PsychExperiment\Emotional';
imageTwoVarOne = dir([emotionalImageDirectory '\*.jpg']);
imageTwoVarTwo = numel(imageTwoVarOne);
imageseq = randperm(imageTwoVarTwo);

nonemotionalImageDirectory = 'C:\PsychExperiment\NonEmotional';
nonemoimageTwoVarOne = dir([nonemotionalImageDirectory '\*.jpg']);
nonemoimageTwoVarTwo = numel(nonemoimageTwoVarOne);
nonemoimageseq = randperm(nonemoimageTwoVarTwo);

for i=1:ntrials
    idxemo = imageseq(i);
    idxnonemo = nonemoimageseq(i);
    loadimageTwo = imread(imageTwoVarOne(idx).name);
    nonemoloadimageTwo = imread(nonemoimageTwoVarOne(idx).name);
    % Now display the two images for this trial?
end