about random again

2012 6 12
1 个回答
6 次查看（30 天）

0 个投票

I have one matrix as follows X = rand(4,10)
I want to generate a matrix from X and in each row a variable should be randomly selected and all possible combination can be used. actually the following code works for a small set like d = rand(4,3) but i have problem when a larger set like above X = rand(4,10) used , please run this and let me know .
[m,n] = size(x);
df = bsxfun(@plus,fullfact(m*ones(1,n)),(0:n-1)*m);
k = randperm(size(df,1));
out = x(df(k(1:min(100,numel(k))),:));

3 个评论
显示 1更早的评论 隐藏 1更早的评论

Niki
Niki 2012-6-12
actually I have solved my problem in another way, but I am very interested to see how to amend this function
Walter Roberson
Walter Roberson 2012-6-12
Perhaps you could describe the "problem" ?
Niki
Niki 2012-6-12
Yes,
actually when I generate my matrix like for example follows
X = rand(10,23)
then i get the size of my matrix
[m,n] = size(X);
then I do
df = bsxfun(@plus,fullfact(m*ones(1,n)),(0:n-1)*m);
I will get error as
??? Error using ==> zeros
Maximum variable size allowed by the program is exceeded.
Error in ==> fullfact at 33
design = zeros(ssize,cols,class(levels));

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Walter Roberson
Walter Roberson 2012-6-12

0 个投票

If I calculate correctly, fullfact(m*ones(1,n)) creates m^n rows of output each of width n.
When X = rand(10,23) then you are asking for 10^23 rows each of width 23, and each element takes 8 bytes (double precision), so you are asking for (8*23) * 10^23 bytes of output. That would be about 2^84 bytes. That exceeds the largest variable that can be handled on a 64 bit operating system (2^64 bytes).

1 个评论
显示 -1更早的评论 隐藏 -1更早的评论

Niki
Niki 2012-6-12
so what should I do to prevent such problem?
can you help me ?

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Creating and Concatenating Matrices 的更多信息

标签

提问:

Niki
Niki
2012-6-12

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by