Select random elements from three consecutive columns in a big matrix?

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AM-Laurentian
AM-Laurentian 2019-4-4
评论： AM-Laurentian 2019-4-5
Hello all,
I have a 12 by 12 matrix, and I want to select 10 random elements. The elements should be from only three consecutive columns.
For example, I want to use 10 random elements from columns (1, 2, 3) or they could be from columns (2, 3, 4) or columns(3, 4, 5) and so on.
Any help please.
Thanks
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Guillaume
Guillaume 2019-4-5
编辑：Guillaume 2019-4-5
Please do not ask the same question twice.
Duplicate of https://www.mathworks.com/matlabcentral/answers/454534-select-elements-from-only-three-consecutive-columns
And it looks like you delete your question once answered, which is not going to go down well with us (and will be restored anyway).
AM-Laurentian
AM-Laurentian 2019-4-5
I am really sorry, it was a mistake. I realized that the question was submitted twice, I tried to delete it as soon as it was submitted but I could not. I apologies for any inconvenience.

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回答（2 个）

Walter Roberson
Walter Roberson 2019-4-5
N = 10;
[r, c] = size(YourMatrix);
start_col = randi([1, c-2]);
chosen = YourMatrix(start_col * r - 1 + randi([1 3*r], 1, N));
Jos (10584)
Jos (10584) 2019-4-5
编辑：Jos (10584) 2019-4-5
M = magic(5) % input data
N = 4 % number of selections
nC = 3 % number of consecutive columns
% engine
szM = size(M)
r = randi(szM(1), N, nC) % N x 3 random rows
c = randi(szM(2) - nC + 1, N, 1) % N random first columns
c = c + [0:nC-1] % add consecutive columns
R = M(sub2ind(szM, r, c)) % index into M

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