Create vector with unique values
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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)
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Accepted Answer
David Hill
on 31 Mar 2022
Edited: David Hill
on 31 Mar 2022
v=1+rand(1,5000);
1 Comment
Bruno Luong
on 31 Mar 2022
Edited: Bruno Luong
on 31 Mar 2022
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.
More Answers (2)
Bruno Luong
on 31 Mar 2022
Edited: Bruno Luong
on 31 Mar 2022
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
% check
all(r>=1 & r<=2)
length(unique(r))==length(r)
4 Comments
Bruno Luong
on 31 Mar 2022
Edited: Bruno Luong
on 31 Mar 2022
Yes, you point correctly unique sort the random stream.
+1 Good point alsoo using 'stable' option and avoid randperm.
Bruno Luong
on 31 Mar 2022
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
Bruno Luong
on 31 Mar 2022
Edited: Bruno Luong
on 31 Mar 2022
% 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)
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