How can I keep just the arrays with 2 is before 3 after random swap 2 numbers.

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Hang Vu 2019-4-17

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评论： Jan 2019-4-19

采纳的回答： Jan

with: s=[1,2,3,4,5];

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madhan ravi 2019-4-17

Show how your output should look like.

Hang Vu 2019-4-17

Thanks for response! the output should be s=[1,4,2,3,5] or [2,4,1,5,3] for example. just to make sure 2 before 3

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Answer 1

Jan 2019-4-17

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编辑：Jan 2019-4-17

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s = [1,2,3,4,5];
s = s(randperm(numel(s)));     % Random permutation?
% Or swap 2 elements:
index = randperm(numel(s), 2);
s(index) = s(flip(index));
s(s == 2 | s == 3) = [2, 3];   % Re-order the elements 2 and 3

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Hang Vu 2019-4-18

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Thank you for the re order idea! I applied for this:

s=[1,2,3,4,5];
L=size(s,2);
a=randi([1 L-1],1);
b=randi([1 L-1],1);
   
temp=s(a);
s(a)=s(b);
s(b)=temp
for i=1:5
    ind1=find(s(:,:)==2);
    ind2=find(s(:,:)==3);
end
if ind1>ind2
    s(s == 2 | s == 3) = [2, 3];
    s
else
    s
end

Jan 2019-4-19

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This is not useful:

for i=1:5
    ind1=find(s(:,:)==2);
    ind2=find(s(:,:)==3);
end

The body of the loop is calculated 5 times with identical values. You can omit the loop:

ind1=find(s(:,:)==2);
ind2=find(s(:,:)==3);

But you can omit this test completely. This is sufficient for all cases:

s(s == 2 | s == 3) = [2, 3];

Why do you use L-1 in randi([1 L-1],1) ? I assume you want L instead.

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Answer 2

Raj 2019-4-17

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Try this:

s=[1,2,3,4,5]
%First random swap
x=randi([1,4],1,1);
if s(x)~=2
   s([x x+1])= s([x+1 x]);
else
    s([x x-1])=s([x-1 x]);
end
disp('After first random swap s=')
disp(s);
%second random swap
y=randi([1,4],1,1);
if s(y)~=2
   s([y y+1])= s([y+1 y]);
else
    %Do nothing
end
disp('After second random swap s=')
disp(s);