Pseudorandom sequence with NO MORE than two consecutive numbers
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Hi everyone.
I want to create an array of numbers from 1 to 4 with a pseudorandom order. A column has 100 rows, and each number must be five times in a subgroup of 20 rows. Additionally, the same number appears in two consecutive rows at the most.
The solution that I found here ( https://es.mathworks.com/matlabcentral/answers/743412-how-to-randomize-trials-without-presenting-the-same-trial-consecutively ), has the main problem that in a subset of 4 rows you can predict which number is the 4th.
Avoiding a while would be unbelievable so that my desired final matrix will be 100x10
Here I drop a short example what I need:
Correct pseudorandomization:
2 3 4 3 3 1 2 4 1 3 3 1 2 4 2 1 1 4 2 4...
Incorrect:
4 3 1 2 4 1 3 2 2 4 3 1 4 3 2 1 2 3 4 1...
any help will be welcome.
2 Comments
Dyuman Joshi
on 12 Jan 2024
"Additionally, the same number appears in two consecutive rows at the most."
Do you mean column instead of rows?
Pablo
on 12 Jan 2024
Answers (3)
% Create the matrix
randomMatrix = createRandomMatrix();
% Display the first 20 rows of the matrix
disp(randomMatrix(1:20,:))
function matrix = createRandomMatrix()
numRows = 100;
numColumns = 10;
numGroups = 5;
values = 1:4;
% Preallocate the matrix
matrix = zeros(numRows, numColumns);
for col = 1:numColumns
% Repeat for each subgroup of rows
for group = 1:numGroups
isValid = false;
while ~isValid
% Generate a random permutation of the numbers for this subgroup
subgroup = repmat(values, 1, numRows/(numGroups*length(values)));
subgroup = subgroup(randperm(length(subgroup)));
% Check the no more than two consecutive numbers condition
for i = 3:length(subgroup)
if subgroup(i) == subgroup(i-1) && subgroup(i) == subgroup(i-2)
break;
end
end
% If we reached the end without breaking, the subgroup is valid
if i == length(subgroup)
isValid = true;
end
end
% Fill the subgroup into the matrix
matrix((group-1)*numRows/numGroups+1:group*numRows/numGroups, col) = subgroup;
end
end
end
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
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1 Comment
@Pablo Check this out.
% Create the matrix
randomMatrix = createRandomMatrix();
% Display the first 20 rows of the matrix
disp(randomMatrix(1:20,:))
function matrix = createRandomMatrix()
numRows = 100;
numColumns = 10;
numGroups = 5;
values = 1:4;
% Preallocate the matrix
matrix = zeros(numRows, numColumns);
for col = 1:numColumns
for group = 1:numGroups
isValid = false;
while ~isValid
% Generate a random permutation of the numbers for this subgroup
subgroupSize = numRows/(numGroups*length(values));
subgroup = repmat(values, 1, subgroupSize);
subgroup = subgroup(randperm(length(subgroup)));
% Check that no more than two consecutive numbers are the same
isValid = true;
for i = 3:length(subgroup)
if subgroup(i) == subgroup(i-1) && subgroup(i) == subgroup(i-2)
isValid = false;
break;
end
end
end
% Fill the subgroup into the matrix
startRow = (group-1)*numRows/numGroups + 1;
endRow = group*numRows/numGroups;
matrix(startRow:endRow, col) = subgroup;
end
end
end
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
If you find the solution helpful and it resolves your issue, it would be greatly appreciated if you could accept the answer. Also, leaving an upvote and a comment are also wonderful ways to provide feedback.
Professional Interests
- Technical Services and Consulting
- Embedded Systems | Firmware Developement | Simulations
- Electrical and Electronics Engineering
Feel free to contact me.
1 Comment
Pablo
on 13 Jan 2024
@Pablo Check this out.
% Create and display the matrix
randomMatrix = createRandomMatrix();
disp(randomMatrix(1:40,:));
function randomMatrix = createRandomMatrix()
numRows = 100;
numColumns = 10;
values = 1:4;
% Preallocate the matrix
randomMatrix = zeros(numRows, numColumns);
for col = 1:numColumns
% Initialize the column
col_data = [];
while length(col_data) < numRows
% Shuffle the values and add them to the column
shuffledValues = values(randperm(length(values)));
col_data = [col_data, shuffledValues];
% Check if the last three elements are the same, if so, remove them
if length(col_data) > 2 && col_data(end) == col_data(end-1) && col_data(end) == col_data(end-2)
col_data(end-2:end) = [];
end
end
% Assign the generated column data to the matrix
randomMatrix(:, col) = col_data(1:numRows).';
end
end
-----------------------------------------------------------------------------------------------------------------------------------------------------------
If you find the solution helpful and it resolves your issue, it would be greatly appreciated if you could accept the answer. Also, leaving an upvote and a comment are also wonderful ways to provide feedback.
Professional Interests
- Technical Services and Consulting
- Embedded Systems | Firmware Developement | Simulations
- Electrical and Electronics Engineering
Feel free to contact me.
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