what is the single command?????????

Question

VIJAY 2018-8-17

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https://ww2.mathworks.cn/matlabcentral/answers/415262-what-is-the-single-command

评论： VIJAY 2018-8-20

I want to create matrix size is 100*12. Each row contain only 5 zeros other elements are 1. for ex

A=[1 1 1 0 0 1 1 0 0 0 1 1 ;
   0 0 1 1 0 0 1 1 0 1 1 1;]

Note: Nobody row is repeated

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Stephen23 2018-8-17

编辑：Stephen23 2018-8-17

在 MATLAB Online 中打开

[zeros(100,5),ones(100,7)]

VIJAY 2018-8-17

thank you guy but rows are repeated.........

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Answer 1

Stephen23 2018-8-17

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https://ww2.mathworks.cn/matlabcentral/answers/415262-what-is-the-single-command#answer_333145

编辑：Stephen23 2018-8-17

在 MATLAB Online 中打开

R = 100; % rows
C = 12;  % columns
N = 5;   % number of 1's.
cmb = nchoosek(1:C,N);  % all unique column combinations.
idx = randperm(size(cmb,1)); % indices to randomize combinations.
idc = cmb(idx(1:R),:); % (col index) pick first 100 random combinations.
idr = ndgrid(1:R,1:N); % (row index).
mat = ones(R,C);       % preallocate output matrix.
mat(sub2ind([R,C],idr,idc)) = 0

Check:

>> all(sum(mat,2)==7) % all rows sum to seven.
ans = 1
>> all(ismember(mat(:),0:1)) % only 0's and 1's.
ans = 1
>> size(unique(mat,'rows')) % all rows are unique.
ans =
   100    12

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VIJAY 2018-8-17

thank you .......

Stephen23 2018-8-17

@VIJAY: I hope that it helps. Remember to accept the answer. Accepting my answer is the easiest way to thank me.

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Answer 2

Rik 2018-8-17

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https://ww2.mathworks.cn/matlabcentral/answers/415262-what-is-the-single-command#answer_333148

在 MATLAB Online 中打开

First generate all combinations, and then select 100 from them:

total_row_length=12;
number_of_zeros=5;
selected_number_of_rows=100;
v=1:total_row_length;
col_positions = nchoosek(v,number_of_zeros);
row_positions=repmat((1:size(col_positions,1))',1,size(col_positions,2));
out=ones(size(col_positions,1),total_row_length);
inds=sub2ind(size(out),row_positions,col_positions);
out(inds)=0;
%select a random sample from all possible rows
selected_rows=randperm(size(out,1),selected_number_of_rows);
result=out(selected_rows,:);

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Stephen23 2018-8-17

编辑：Stephen23 2018-8-17

@Star Strider: can you please give explanations for your votes, rather than just disappearing without comment. I am interested to know what you found in Rik Wisselink's answer, that you felt was missing in mine (they are almost identical). Many thanks!

VIJAY 2018-8-20