# Random shuffle of vector elements

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Premysl Stastny2021-10-5

Hello,
How to randomly shuffle all elements of the vector except the first and last position?
For example:
I have vector A=[5 1.5 1.6 1.7 5] and I want to randomly shuffle 2nd, 3rd 4th element while the 1st and the last will stay the same.
Thank you

### 采纳的回答

This can be easily done by addressing the vector correctly. First you need a random order to shuffle your elements. You can do that by using rand and then sort:
[a,b]=sort(rand(1,3))
a = 1×3
0.0591 0.2095 0.2737
b = 1×3
3 2 1
so b will be the order. Now you need to use that to re-order your vector, let's call the new vector A2:
A=[5 1.5 1.6 1.7 5];
A2 = [A(1) A(b+1) A(end)]
A2 = 1×5
5.0000 1.7000 1.6000 1.5000 5.0000
Now you have a new vector with the first and last same as they were, but 2:4 have been randomly shuffled.
Hope this solves your question.

### 更多回答（1 个）

Fangjun Jiang 2021-10-5
p=randperm(3);
index=[1,1+p,5];
b=A(index);
##### 1 个评论显示隐藏 无
Fangjun Jiang 2021-10-5
do it in one shot
p=perms(2:4);
index=[ones(6,1), p, 5*ones(6,1)];
b=A(index)

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