Equal Sized random assortment, using randi?

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Chris Keightley 2021-5-2

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评论： Chad Greene 2021-5-3

Hello everyone,

I have used the following code to generate a matrix of random integers (1's and 2's). However, I am finding myself with an unequal amount of random integers in each column (e.g., eleven "1's" and eight "2's" in some columns). I would like to know how I could get a fixed amount of equally sized conditions using this function. In where, I could get ten "1's" and ten "2's" equally spread among all six columns, that still maintains a random order. Am I using the right function (randi) to do accomplish this? Please let me know if I am unclear with my question.

Kind regards,

T = [ ];
ii=1;
while ii<=20;
    T(ii,:)= randi(2,1,8);
    ii=ii+1;
end;

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Answer 1

Image Analyst 2021-5-2

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Chris: first you need to create a column vector with the desired number of 1s and 2s in the column. Then you need to use randperm() to scramble the order and stick it in your output array:

num1s = 10; % Whatever you want
num2s = 10; % Whatever you want
% Make a column vector with the specified number of 1s and 2s in it.
unscrambled = [ones(num1s, 1); 2 * ones(num2s, 1)]
rows = length(unscrambled);
columns = 16; % Whatever you want
output = zeros(rows, columns);
% Scramble and place into the output matrix.
for col = 1 : columns
	sortOrder = randperm(rows);
	output(:, col) = unscrambled(sortOrder);
end
output % See it in the command window.

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Image Analyst 2021-5-2

编辑：Image Analyst 2021-5-2

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Chad, I don't understand what you're saying. If I change it to have

num1s = 4; % Whatever you want
num2s = 3; % Whatever you want
% Make a column vector with the specified number of 1s and 2s in it.
unscrambled = [ones(num1s, 1); 2 * ones(num2s, 1)]
rows = length(unscrambled);
columns = 9; % Whatever you want
output = zeros(rows, columns);
% Scramble and place into the output matrix.
for col = 1 : columns
	sortOrder = randperm(rows);
	output(:, col) = unscrambled(sortOrder);
end
output % See it in the command window.