How to randomise numbers in a vector?

Thank you very much for your help. The second option works wonders! I am trying to randomise the subconditions of the main conditions of my experiment - in order for me to do so, there is one last step I need to figure out. I understand if this post is becoming a bit too lengthy for you but, if not, could you please be so kind as to help me understand one more thing? If yes, please see the file attached.

counterbalancing(:,1)= participant ID
counterbalancing(:,2)= speed levels (1, 2, 3) 
counterbalancing(:,3)= conditions (1, 2, 3, 4) per speed level

What I am trying to do is, for every speed level (column 2) per participant (column 1), to randomise the 4 speed level subconditions (column 3) - i.e. to randomise the first 4 rows containing 1, 2, 3, 4 and then the next 4 rows containing 1, 2, 3, 4 and so on and so forth, until the end of the matrix. I very vaguely remember there is a simple of doing computations on every n rows at a time, which doesn't require for loops or anything of the sort.

Jan 2016-12-19

编辑：Jan 2016-12-19

在 MATLAB Online 中打开

Y  = reshape(X(:, 3), 4, [])
YS = Shuffle(Y, 1);  % Mix columns
X(:, 3) = YS(:);

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Answer 2

Andrei Bobrov 2016-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/317259-how-to-randomise-numbers-in-a-vector#answer_247621

编辑：Andrei Bobrov 2016-12-17

在 MATLAB Online 中打开

Hi Elena!

One way:

x= [1 1; 1 2; 1 3; 1 4]
[~,ii] = sort(rand(size(x,1),1));
out = x(ii,:);

or just

out = x(randperm(size(x,1)),:);

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Jan 2016-12-18

编辑：Jan 2016-12-18

randperm uses the Fisher-Yates shuffle now (as FEX: Shuffle), which is more accurate than SORT(RAND). The later is a stable sort, so if two elements replied by RAND are equal (unlikely, but not impossible) the sorting order is not random. If you e.g. have to shuffle a vector of 2^52 elements, uuhm, well... Who cares.

Bianca Elena Ivanof 2016-12-18