Create vector with unique values

I need to create a vector of length 5000 in the interval from 1 to 2 with unique values ​​(so that there are no repetitions), is it possible to do this? (the randi command gives me the values, but there appear repetitions)

Answer 1

[David Hill]

v=1+rand(1,5000);

[Bruno Luong]

You can't be sure there is no repetition, especially consider the number of floating point numbers in (0,1) and generate by rand() on a computer are finite (but large), but I admit the chance is tiny.

Answer 2

[Bruno Luong]

Rejection method, it likely needs a single iteration

n = 5000;
while true
    r = unique(1+rand(1,round(n*1.1)));
    p = length(r);
    if p >= n
        r = r(randperm(p,n));
        break
    end
end
r

r = 1×5000

1.0939 1.1626 1.1336 1.1551 1.2421 1.0354 1.5319 1.3017 1.2257 1.9326 1.8532 1.9819 1.9699 1.2436 1.2587 1.9323 1.9716 1.1154 1.2823 1.7038 1.7327 1.1640 1.9592 1.9968 1.1904 1.6269 1.1277 1.5514 1.2853 1.3155

% check
all(r>=1 & r<=2)

ans = logical
   1

length(unique(r))==length(r)

ans = logical
   1

[Les Beckham]

I think this is the most correct approach.

Just curious, though, @Bruno Luong, why do the randperm "scrambling" of r? Couldn't you just take the first n elements since r is already random?

[Les Beckham]

Actually, I forgot that unique sorts by default. One could use

r = unique(1+rand(1,round(n*1.1)), 'stable');

to avoid the sorting and then just truncate the result to the first n elements.

[Bruno Luong]

Yes, you point correctly unique sort the random stream.

+1 Good point alsoo using 'stable' option and avoid randperm.

[Bruno Luong]

Here is complete code with modification suggested by @Les Beckham

n = 5000;
while true
    r = unique(1+rand(1,round(n*1.1)),'stable');
    p = length(r);
    if p >= n
        r = r(1:n);
        break
    end
end

Answer 3

[Bruno Luong]

% I'm sure there is no repetition but the set of values is not random

r = 1+randperm(5000)/5000;

% check
all(r>=1 & r<=2)
length(unique(r))==length(r)