# How to re-arrange swapped elements in an estimated vector as compared to a reference vector

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Sadiq Akbar on 13 Nov 2019
Commented: Sadiq Akbar on 16 Nov 2019
I have a reference vector u=[0.5 1 1.5 0.6981 1.3962 1.5707].
I estimate several vectors of the same size using a metaheuristic algorithm. But the problem is that sometimes the algorithm gives me vectors in which the positions of elements are swapped and sometimes there is no change in the positions i.e. sometimes positios of 1st and 2nd elements are interchanged, sometimes positions of 1st and 3rd elemtns are interchnaged and sometimes positions of 2nd and 3rd eleents are interchanged with each other in the estimated vectors.And if the changes ocuurs in the positions of two elements in the 1st three elements, the same change occurs in the last three elements also.But sometimes the positions are not interchnaged in the estimated vectors. I want to re-arrange the estimated vector elements if they interchange their positions. What check should I keep on the positions of the elements of the estimated vectors. Regards,

Johannes Fischer on 13 Nov 2019
How do you determine you that two values have swapped position?
the cyclist on 13 Nov 2019
Expanding on Johannes' question a bit:
You need to explain the exact rule for swapping elements. Give a small, representative example of what the inputs and outputs would be for what you want to do.
Keep in mind that the only thing we know about the problem you are trying to solve is what you tell us here.
Sadiq Akbar on 13 Nov 2019
I use Flower Pollination Algorithm. My work is to estimate my reference vector.
u=[0.5 1 1.5 0.6981 1.3962 1.5707]
When I run the algorithm, it gives me an estimated vector like
Est1=[0.499 1.002 1.5001 0.6890 1.3880 1.49998]
In this there is no change in the position of any element. But when I run it again, It gives me
Est2=[0.9999 0.5001 1.49999 1.3990 0.6999 1.5880]
As you can see here the position of 1st and 2nd elements are interchanged in Est2 as compared to u. Likewise when I run it again, it gives me
Est3=[0.5001 1.4981 1.0012 0.70001 1.57160 1.39990]
Here the positions of 2nd and 3rd elemnts are interchanged and so on. As is clear when there is no change of positions in two of the the 1st three elements, then no change occurs in the positions of the last three elements also as is clear in Est1. But when the 1st and 2nd elements interchange their positions in the 1st three elements, then the same happens pattern is followed in the last three elements also as in Est2. And the same can be observed in Est3. I want to rearrange these positions on the pattern of my vector u even if the algorithm gives me Est vector having changed positions.
Regards,

the cyclist on 16 Nov 2019
Here is a different approach. It relies on the fact that you want the first three inputs to be in ascending numeric order, and ignores whether they are close to [0.5, 1.0, 1.5].
% Define indices for convenience
half_1st = 1:3;
half_2nd = 4:6;
% Reference vector
u=[0.5 1 1.5 0.6981 1.3962 1.5707];
% Some of the inputs
temp = [ ...
1.4293 1.6429 0.1220 1.3833 1.5643 0.7691
1.0385 0.5639 0.5502 1.5833 1.4221 1.5648
0.6842 1.4170 0.1005 1.3988 1.5756 0.0398
0.0156 1.3050 0.9022 0 1.5700 1.3977
0.7765 0.0962 1.3453 1.4011 0.7075 1.5688
1.2783 0.0559 1.1249 1.5817 0.4605 1.3814];
% Loop over the sample inputs
for nn = 1:6
[sortTemp, sortIndex] = sort(temp(nn,half_1st));
two(nn,:) = temp(nn,[half_1st(sortIndex) half_2nd(sortIndex)]);
end
I hope this one works for you.

#### 1 Comment

Sadiq Akbar on 16 Nov 2019
Thank you very much the cyclist. Indeed it worked. I am really very thankful to your heartedly help. Regards,

### More Answers (2)

the cyclist on 13 Nov 2019
Edited: the cyclist on 13 Nov 2019
% Inputs
u=[0.5 1 1.5 0.6981 1.3962 1.5707];
Est1=[0.499 1.002 1.5001 0.6890 1.3880 1.49998];
Est2=[0.9999 0.5001 1.49999 1.3990 0.6999 1.5880];
Est3=[0.5001 1.4981 1.0012 0.70001 1.57160 1.39990];
% Define a few parameters for convenience
half_1st = 1:3;
half_2nd = 4:6;
tol = 0.01;
% Find the elements of Est1, etc, that are near u
% EDITED for a mistake in the ordering of the ismembertol arguments
[tf1,idx1] = ismembertol(u(half_1st),Est1(half_1st),tol);
[tf2,idx2] = ismembertol(u(half_1st),Est2(half_1st),tol);
[tf3,idx3] = ismembertol(u(half_1st),Est3(half_1st),tol);
% Define the rearranged vectors
Est1_new = Est1([half_1st(idx1) half_2nd(idx1)]);
Est2_new = Est2([half_1st(idx2) half_2nd(idx2)]);
Est3_new = Est3([half_1st(idx3) half_2nd(idx3)]);

Show 8 older comments
Sadiq Akbar on 15 Nov 2019
Thank you veru much for your help. But aghain I got the same error as above. Let me re-explain my problem.
My reference vector
u=[0.5 1 1.5 0.6981 1.3962 1.5707];
I am using an Algorithm "Flower Pollination" which returns me a vector of the same size as u. This returned vector is my estimated vector. I run this algorithm 100 times and each time I get an estimated vector of the same size as u. For this iteration, I have set up a for loop like this:
for n=100:199
[out1,out2,out3]=flower(n,Remaining input arguments---)
temp(nn,:)=out1;
------------
-----------
%-------------Check for swapping-----------------
if abs((temp(nn,1)-u(2)))< abs((temp(nn,1)-u(1)))
two(nn,:)=[temp(nn,2) temp(nn,1) temp(nn,3) temp(nn,5) temp(nn,4) temp(nn,6)];
elseif abs((temp(nn,1)-u(3)))< abs((temp(nn,1)-u(1)))
two(nn,:)=[temp(nn,3) temp(nn,2) temp(nn,1) temp(nn,6) temp(nn,5) temp(nn,4)];
elseif abs((temp(nn,2)-u(3)))< abs((temp(nn,1)-u(1)))
two(nn,:)=[temp(nn,1) temp(nn,3) temp(nn,2) temp(nn,4) temp(nn,6) temp(nn,5)];
else
two(nn,:)=temp(nn,:);
end
end
But when I run this code, and check the 100 estimated vectors. In some of these vectors, positions of estimated elements have been interchanged and in some of these vectors there is no position interchange.If the change ocuurs, its like this: Positions 1 and 2 interchange
Positions 1 and 3 interchange
Positions 2 and 3 interchange
Then I manually re-arrrange those estimated vectors.I want that Matlab should check each of them in advance and re-arrange them automatically before displaying them. Regards
the cyclist on 15 Nov 2019
I beileve I understand your problem.
In an earlier comment, I already explained why your algorithm doesn't quite work. Let me try again, with a simple example where it fails. Look at this:
% Inputs
u=[0.5 1 1.5 0.6981 1.3962 1.5707];
temp = [1.49999 0.9999 0.5001 1.5880 1.3990 0.6999];
nn = 1;
abs((temp(nn,1)-u(2))) < abs((temp(nn,1)-u(1))) % This is the first line of your algorithm.
Your algorithm is testing if element 2 of u is closer than element 1. It is! So, you swap elements 1 and 2, and you are done.
But that is wrong in this case. Element 3 is even closer. You actually want to swap elements 1 and 3.
So, I think you should try to fix your testing cases so that you cover this possibility.
the cyclist on 15 Nov 2019
Regarding my solution, you keep saying it does not work, and reporting the error that MATLAB is reporting. But have you tried to understand why you are getting that error, or how my solution should work in the first place?
I suggest you try adjusting the tolerance value, which might be too small. Maybe try setting
tol = 0.1; % Instead of tol = 0.01
and see if that solves it.

Sadiq Akbar on 15 Nov 2019
Edited: the cyclist on 15 Nov 2019
half_1st = 1:3;
half_2nd = 4:6;
tol = 0.1;
u=[0.5 1 1.5 0.6981 1.3962 1.5707];
nn=0;
for n=100:199
nn=nn+1;
[out1,out2,out3]=flower(n,Remaining input arguments---)
temp(nn,:)=out1;
------------
-----------
%-------------Check for swapping-----------------
[tf,idx] = ismembertol(u(half_1st),temp(nn,half_1st),tol);
two(nn,:) = temp(nn,[half_1st(idx) half_2nd(idx)]);
end
When I run the above code, I get the following error even though I have reduced value of tol to 0.1 as per your instruction:
Subscript indices must either be real positive integers or logicals.
Error in servertestingMathworks (line 26)
two(nn,:) = temp(nn,[half_1st(idx) half_2nd(idx)]);

the cyclist on 15 Nov 2019
Can you post the value of out1 for which this algorithm does not work?
Sadiq Akbar on 15 Nov 2019
I ran it several times,and each time I get different values of out1 given below:
1.4293 1.6429 0.1220 1.3833 1.5643 0.7691
1.0385 0.5639 0.5502 1.5833 1.4221 1.5648
0.6842 1.4170 0.1005 1.3988 1.5756 0.0398
0.0156 1.3050 0.9022 0 1.5700 1.3977
0.7765 0.0962 1.3453 1.4011 0.7075 1.5688
1.2783 0.0559 1.1249 1.5817 0.4605 1.3814
and so on and each time it gives me the same error
the cyclist on 16 Nov 2019
OK, so it is clear (to me) why my algorithm isn't working. Do you see how your original example input
Est1=[0.499 1.002 1.5001 0.6890 1.3880 1.49998]
Est2=[0.9999 0.5001 1.49999 1.3990 0.6999 1.5880]
Est3=[0.5001 1.4981 1.0012 0.70001 1.57160 1.39990]
the values are all very close to [0.5 1.0 1.5]? The biggest discrepancy is only about 0.002! I assumed that that was always true, but your new inputs
1.4293 1.6429 0.1220 1.3833 1.5643 0.7691
1.0385 0.5639 0.5502 1.5833 1.4221 1.5648
0.6842 1.4170 0.1005 1.3988 1.5756 0.0398
0.0156 1.3050 0.9022 0 1.5700 1.3977
0.7765 0.0962 1.3453 1.4011 0.7075 1.5688
1.2783 0.0559 1.1249 1.5817 0.4605 1.3814
can be much further away from [0.5 1.0 1.5].
Neither my algorithm nor your algorithm, which both rely on proximity to the original vector, will work for this input. I have another idea that I will post later.