How to present randomly 70 different images on 70 different trials from a set of 161 images which is stored in a particular folder ?

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ANKIT MAURYA 2023-1-14

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编辑： dpb 2023-1-16

I have a folder which consists of 161 images. I want to run total 70 trials and want to present different images on different trials randomly out of these 161 pictures. I have written a code, but not able to understand what is the problem. Kindly help me. I don't know much about programming

The code I wrote is ----

folder = 'F:\Ankit \Bisection_Task \Manipulable_objects'
totalimg = dir(fullfile(folder,  '/*.bmp'));
as = numel(totalimg);
imageseq = randperm(as);
for i=1:70  
    idx = imageseq(i);
    img = imread(totalimg(idx).name);
end

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Answer 1

dpb 2023-1-14

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编辑：dpb 2023-1-14

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Your code works except you're not doing anything inside the loop with each image in turn; you're just reading in and overwriting the img variable every pass so when the loop ends you always have whichever was the last image data in the permuted list.

What is your intent here; show each image to a user and interact with it or do some other processing on each image in turn? Whatever it is, you need to do something with each image before going on to the next INSIDE the loop.

One refinement could be something like

Nselect=70;     % use variable, don't bury "magic numbers" in code
imageseq=randperm(numel(totalimg),Nselect);     % generate the permutation vector
for i=1:Nselsect
  img=imread(totalimg(imageseq(i)).name);
  % now do your thing with this image here, then go on to the next...
  ...
end

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ANKIT MAURYA 2023-1-15

Hi dpb,

Thanks a lot for this. I am able to run the code now perfectly.

I have just another followup query. I am able to present randomly one different image on 70 different trials out of 161 pictures stored in a folder named Manipulable_objects. I want to check which of the one image out of 161 images is presented on each of these 70 trials. It's like, I want to know what/which image is presented on trial by trial basis.

I am just posting chunks of my code here----------

I would appreciate your help and thanks again for resolving my previous query

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%TEST EXPERIMENT PHASE BEGINS%%%%%%%%%%%%%%%%%%%%%%

% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% TRIAL STRUCTURE %%%%%%%%%%%%%%%%%%%%%%%%%%%%

start = GetSecs;

for i_trial = 1:70

% 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);

% Flip to the screen

Screen('Flip', window);

% Wait for 500 ms

WaitSecs (0.5);

%%%%%%%%%%%%% Selecting manipulable image randomly from

%%%%%%%%%%%%% Manipulable_objects folder %%%%%%%%%%%%%%%%%%%%5

folder ='F:\Ankit\2nd Study_Jan_2023\Manipulable_objects'

manipulable_image = dir(fullfile(folder, '/*.bmp'))

as = numel(manipulable_image);

imageseq = randperm (as);

for i=1:as

idx =imageseq(i);

img = imread(fullfile(folder,manipulable_image(idx).name));

end

%%%%%%%%%%%%% Another way of Selecting manipulable image randomly from

%%%%%%%%%%%%% Manipulable_objects folder %%%%%%%%%%%%%%%%%%%%

% folder ='F:\Ankit\2nd Study_Jan_2023\Manipulable_objects'

% fileList = dir(fullfile(folder, '/*.bmp'));

% sortOrder =randperm(length(fileList));

% fileList =fileList(sortOrder);

% for k = 1: length(fileList)

% baseFileName = fileList(k).name;

% fullFileName = fullfile(folder,baseFileName);

% img = imread(fullFileName);

% end

imageTexture =Screen('MakeTexture',window,img); % Convert image into texture

% Draw the rect to the screen

Screen('DrawTexture', window, imageTexture,[],[], 0);

% Flip to the screen

Screen('Flip', window);

WaitSecs (Delay_time (i_trial)); % random durations for which images to be presented on screen

DrawFormattedText(window, 'Closer to Shorter or Longer duration?', 'center', 'center', white); % Question asked to Participants

Screen('Flip', window)

%%%%%%%% Accepting mouse responses from Participants %%%%%%%%%%%%%%

%%%%%% SHORT = 1 [left mouse button]; LONG = 2 [right mouse button]%%%%%%%%%

while 1

[x1,y1,buttons,~,~,~] = GetMouse();

if buttons(1)== 1

Mouse_Button_Pressed(i_trial)= 1 ;

break;

end

if buttons(3) == 1

Mouse_Button_Pressed(i_trial)= 2 ;

break;

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Creating data matrix%%%%%%%%%%%%%%%%%%%%%%

data = zeros (70,5); % data is a variable that will take up the value of Delay_time and Key_Pressed

data(:,1)= sub_no;

data(:,2)= Trial_Number;

data(:,3)= Delay_time*1000; % ':' is for the row and 1 is the 1st column

data(:,4)= Mouse_Button_Pressed; % ':' is for the row and 2 is the 2nd column

data(:,5)= Condition;

currentFolder = pwd;

% pwd- present working directory

dbase = strcat(currentFolder,'\Subject_', sub_name,'_',num2str(sub_no),'_Mains_Exp_Hand','.xls');

% dbase is a variable where particular file with particular name and number is saved

a = xlswrite((dbase), data); % Write the data into 'csv' file

T = array2table(data,'VariableNames',{'Subject No.','Trial_No.','Stim_dur(ms)','Response_Button','Condition'}); % converts the 'data' named matrix into table form and then add titles/headlines to each of the variables

writetable (T,(dbase)) % writes that table into output file

% Clear the screen

sca;

ANKIT MAURYA 2023-1-15

This one ------------------------------

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%TEST EXPERIMENT PHASE BEGINS%%%%%%%%%%%%%%%%%%%%%%

% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% TRIAL STRUCTURE %%%%%%%%%%%%%%%%%%%%%%%%%%%%

start = GetSecs;

for i_trial = 1:70

% 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);

% Flip to the screen

Screen('Flip', window);

% Wait for 500 ms

WaitSecs (0.5);

%%%%%%%%%%%%% Selecting manipulable image randomly from

%%%%%%%%%%%%% Manipulable_objects folder %%%%%%%%%%%%%%%%%%%%5

folder ='F:\Ankit\2nd Study_Jan_2023\Manipulable_objects'

manipulable_image = dir(fullfile(folder, '/*.bmp'))

as = numel(manipulable_image);

imageseq = randperm (as);

for i=1:as

idx =imageseq(i);

img = imread(fullfile(folder,manipulable_image(idx).name));

end

%%%%%%%%%%%%% Another way of Selecting manipulable image randomly from

%%%%%%%%%%%%% Manipulable_objects folder %%%%%%%%%%%%%%%%%%%%

% folder ='F:\Ankit\2nd Study_Jan_2023\Manipulable_objects'

% fileList = dir(fullfile(folder, '/*.bmp'));

% sortOrder =randperm(length(fileList));

% fileList =fileList(sortOrder);

% for k = 1: length(fileList)

% baseFileName = fileList(k).name;

% fullFileName = fullfile(folder,baseFileName);

% img = imread(fullFileName);

% end

imageTexture =Screen('MakeTexture',window,img); % Convert image into texture

% Draw the rect to the screen

Screen('DrawTexture', window, imageTexture,[],[], 0);

% Flip to the screen

Screen('Flip', window);

WaitSecs (Delay_time (i_trial)); % random durations for which images to be presented on screen

DrawFormattedText(window, 'Closer to Shorter or Longer duration?', 'center', 'center', white); % Question asked to Participants

Screen('Flip', window)

%%%%%%%% Accepting mouse responses from Participants %%%%%%%%%%%%%%

%%%%%% SHORT = 1 [left mouse button]; LONG = 2 [right mouse button]%%%%%%%%%

while 1

[x1,y1,buttons,~,~,~] = GetMouse();

if buttons(1)== 1

Mouse_Button_Pressed(i_trial)= 1 ;

break;

end

if buttons(3) == 1

Mouse_Button_Pressed(i_trial)= 2 ;

break;

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Creating data matrix%%%%%%%%%%%%%%%%%%%%%%

data = zeros (70,5); % data is a variable that will take up the value of Delay_time and Key_Pressed

data(:,1)= sub_no;

data(:,2)= Trial_Number;

data(:,3)= Delay_time*1000; % ':' is for the row and 1 is the 1st column

data(:,4)= Mouse_Button_Pressed; % ':' is for the row and 2 is the 2nd column

data(:,5)= Condition;

currentFolder = pwd;

% pwd- present working directory

dbase = strcat(currentFolder,'\Subject_', sub_name,'_',num2str(sub_no),'_Mains_Exp_Hand','.xls');

% dbase is a variable where particular file with particular name and number is saved

a = xlswrite((dbase), data); % Write the data into 'csv' file

T = array2table(data,'VariableNames',{'Subject No.','Trial_No.','Stim_dur(ms)','Response_Button','Condition'}); % converts the 'data' named matrix into table form and then add titles/headlines to each of the variables

writetable (T,(dbase)) % writes that table into output file

% Clear the screen

sca;

ANKIT MAURYA 2023-1-16

Hi dpb,

I tried your code but it's repeating the same image again and again on every trial.

KKindly please look the whole code that i sent to you and tell me where is the problem.

Thank You

dpb 2023-1-16

编辑：dpb 2023-1-16

在 MATLAB Online 中打开

You persist in not heeding advice...there's no point in my continuing to tell you the same thing over and over if you're not going to take anything I say to heart.

Since you were producing the randomized images before, then you've broken something else, not that part....and you don't have my code in there, anyway...so, look for something else that you've changed.

There's no difference in the use of

imagseq=randperm(as);

and

imagseq=randperm(as,Nselect);

excepting that the latter will have only the number of elements in it to solve your problem of wanting only the 70 elements after the loop is done instead of all 161 from the unconstrained permutation vector. Again, read the docs.

>> randperm(6)      % unconstrained permutation vector
ans =
     2     4     3     6     5     1
>> randperm(6,4)    % select only four out of the six instead...
ans =
     4     6     5     2
>> 

While it's not as clean a solution, you could simply use

imagseq=randperm(as);           % return the whole permutation vector
imageseq=imagseq(1:Nselect);    % keep the number wanted

and be at the same place.

Again, can't urge strongly enough to quit burying magic numbers like the 70 in the code; use variables so they can be changed in one place and use the debugger to find where you've made logic errors...

Good luck...

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How to present randomly 70 different images on 70 different trials from a set of 161 images which is stored in a particular folder ?

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How to present randomly 70 different images on 70 different trials from a set of 161 images which is stored in a particular folder ?

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