Create vector with unique values
显示 更早的评论
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)
采纳的回答
David Hill
2022-3-31
编辑：David Hill
2022-3-31
v=1+rand(1,5000);
1 个评论
Bruno Luong
2022-3-31
编辑：Bruno Luong
2022-3-31
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.
更多回答（2 个）
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 个评论
Les Beckham
2022-3-31
编辑：Les Beckham
2022-3-31
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
2022-3-31
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
2022-3-31
编辑：Bruno Luong
2022-3-31
Yes, you point correctly unique sort the random stream.
+1 Good point alsoo using 'stable' option and avoid randperm.
Bruno Luong
2022-3-31
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
2022-3-31
编辑：Bruno Luong
2022-3-31
% 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)
类别
在 帮助中心 和 File Exchange 中查找有关 Random Number Generation 的更多信息
产品
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
