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

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.

[Davide Masiello]

I guess for such a small matrix it is most convenient to just manually code it, unless you intend to expand your code to more general purposes, in which case it would be helpful to know what the latter are.

[Sai Teja Suggala]

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]

What are typically values of N and M ?

Answer 1

[Bruno Luong]

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

Answer 2

[David Hill]

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

[Bruno Luong]

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.

Answer 3

[Jan]

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