Matrix with repetitions of a vector

Question

Ana Maria Alzate 2019-5-28

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/464398-matrix-with-repetitions-of-a-vector

回答： Jan 2019-5-28

M = [1:8];
A = repmat(M,1,4)

I have these two vector. I need to create a 6x32 matrix with repetitions of the vector A, different to the original.

for i = 2:6
    A(i,:) = A(randperm(length(A)))
 end

I tried this loop, but I need to make sure some conditions:

First matrix, rows have to have different starting number.

Second matrix, it can happen only once that a number is followed by the same number

Third matrix, numbers 5 and 6 cannot be followed by numbers 7 and 8 respectively

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

dpb 2019-5-28

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/464398-matrix-with-repetitions-of-a-vector#answer_376890

在 MATLAB Online 中打开

A=repmat(M,6,4);

is what you say literally, but I don't follow what you mean by "with repetitions of the vector A, different to the original". What is to be "different to the original" and how so?

2 个评论
显示无隐藏无

Ana Maria Alzate 2019-5-28

编辑：Image Analyst 2019-5-28

在 MATLAB Online 中打开

A = repmat(M,6,4)

With this function I was getting repetition of the vector, and I need it to be sorted differently in each row.

A(i,:) = A(randperm(length(A)))

I found this function and it is working, except there are the other conditions, like rows cannot start with the same number, etc.

Image Analyst 2019-5-28

Sounds like homework. Is it? Is so, we need to know so that we don't just give you the complete solution which might get you into trouble.

Do you need help setting up a "while" loop?

请先登录，再进行评论。

Answer 2

Jan 2019-5-28

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/464398-matrix-with-repetitions-of-a-vector#answer_376898

在 MATLAB Online 中打开

This sounds like a homework question, but you did not mention thuis explicitly. The solution is easy, but I do not want to solve your homework.

M = 1:8;  % No square brackets needed, because 1:8 is a vector already
A = repmat(M, 1, 4);
ready = false;
while ~ready
    Result = zeros(6, 32);
    Result(1, :) = A;
    for i = 2:6
        Result(i,:) = A(randperm(numel(A)));
    end
    
    ready = <expression to check the wanted condition>
end

You can use this brute force approach. Fill in a test, if the wanted condition is met.

"rows have to have different starting number": This means, that unique(A(:, 1)) must reply 6 elements.
"it can happen only once that a number is followed by the same number": Use diff(A, 1, 2). Then sum helps to count the zeros. By the way: In which direction is "follow" defined here?
"numbers 5 and 6 cannot be followed by numbers 7 and 8 respectively": Again "follow" is not clear. Use strfind to search for [5,7] and [6,8]. strfind works on row vectors also, but inspite of its name it accepts numerical input also.