Randomize location by trial & reshuffle location if condition not met

I have the following code that allows me to present a stimulus at a location randomly selected from a list of X,Y coordinates 10 times before changing to another randomly selected location. I would like it to 1. present the stimulus at each location 10 times but randomize the location every trial (e.g. Trial 1: X1,Y1; Trial 2: X3, Y3; Trail 3: X7,Y7; Trial 4: X1,Y1; etc. trial count at X1,Y1 = 2 out of 10, all others = 1 out of 10) & 2. reshuffle the tested location into the pool if a condition is not met prior to presentation.

I am thinking this may require me to create a list of all potential trials and have the program randomly pull from that list. Any thoughts or advice would be appreciated.

for k = 1 : numel(X_vector)
    n_trials = 10;

    if strcmp(Testing_Mode,'random')
        idx=randperm(length(X_vector),42);
        x = X_vector(idx(k));
        y = Y_vector(idx(k));
    end
end

Unrecognized function or variable 'X_vector'.

Answer 1

[Divyanshu]

Hi HumbleCoder,

Few pointers to consider for better understanding of the sample script:

• The demo script below takes 6 sample location points and number of trials for each location is 5.
• The script makes use of a dictionary where the keys represent the location which is a string constructed using x & y coordinates.
• The values corresponding to keys are the count of total trials for that location.

Here is the sample script which you can refer to:

x_vec = [0 2 3 7 8 1]';
y_vec = [1 4 5 2 9 6]';
locations = ["01" "24" "35" "72" "89" "16"];
values = [0 0 0 0 0 0];
d = dictionary(locations,values);
for k = 1 : length(x_vec)
    n_trials = 5;
    idx=randperm(length(x_vec),6);
    x = x_vec(idx(k));
    y = y_vec(idx(k));
    temp = string(x) + string(y);
    if(d(temp) >= 5)
        %here put the logic to reshuffle the current location if condition
        %is not met.
    else
        d(temp) = d(temp)+1;
    end
end

Please go through the following documentation for more details on dictionary:

Object that maps unique keys to values - MATLAB (mathworks.com)

[HumbleCoder]

Hi DV, I really appreciate your response. I have been trying your suggestion for a few days and been getting an undefined function/variable error for dictionary. Today it hit me that the function may not be avalible in Matlab 2019a? Am I correct? If i am, do you have an alterative solution for accomplishing my question above? I am hesistant to upgrade my Matlab version.

Thank you again for your help.

[Dyuman Joshi]

Yes, dictionary is available from 2022b and thus you can not access it in 2019a.

You can simply use logical indexing, paired with strcmp in case of the above example posted by Divyanshu.

Also replace

idx=randperm(length(x_vec),6)

with

idx = randi(length(x_vec))

and directly use idx.