How to generate a matrix with entries of -1 and +1 of size N x M where all the columns are unique ?

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Sai Teja Suggala 2022-3-7

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评论： Bruno Luong 2022-3-9

I want to create a matrix of size N x M, where each matrix element can be either -1 or +1 . The matrix must have unique columns

For N = 2, maximum number of 2 sized vectors possible with -1 and +1 are 2^N .

So, for N =2 and M =4

matrix would be

1 1 -1 -1

1 -1 1 -1

So, for a given N and M . I must get said matrix

Thanks a lot before hand.

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Sai Teja Suggala 2022-3-7

Yes @Davide Masiello, I intend to expand it . My N would be 64. For which 2^64 would be my maximum number of columns. But I just want to limit it to say 1000 . Matrix of size ( 64 x 1000) with -1 and +1 as entries..given all columns are unique..

Bruno Luong 2022-3-7

What are typically values of N and M ?

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Answer 1

Bruno Luong 2022-3-7

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编辑：Bruno Luong 2022-3-7

在 MATLAB Online 中打开

N = 3;
M = 5;
A = (dec2bin(randperm(2^N,M)-1,N)-'0')'*2-1
A = 3×5
     1    -1     1     1     1
     1    -1    -1     1    -1
    -1    -1     1     1    -1

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Answer 2

David Hill 2022-3-7

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在 MATLAB Online 中打开

M=10;N=7;
m=unique((-1).^randi(2,2*M,N),'rows')';
m=m(1:N,1:M);

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Bruno Luong 2022-3-9

在 MATLAB Online 中打开

Sorry but you accepted answer is not robust

N=10;
M=2^N; % 1024
m=unique((-1).^randi(2,2*M,N),'rows')';
m=m(1:N,1:M)
Index in position 2 exceeds array bounds. Index must not exceed 893.

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Answer 3

Jan 2022-3-7

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在 MATLAB Online 中打开

N = 3;
M = 8;
R = 1 - 2 * rem(floor(pow2(1-N:0).' .* (0:M-1)), 2)
R = 3×8
     1     1     1     1    -1    -1    -1    -1
     1     1    -1    -1     1     1    -1    -1
     1    -1     1    -1     1    -1     1    -1