find two minimum values not followed by each other.

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FV 2020-4-19

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评论： Ameer Hamza 2020-4-20

I am using mink(A,2) to find the two smallest values, but I need to find the two smallest values not followed by each other. How can this be done?

To illustrate: A(1; 1.2; 1.2; 0.7; 0.6; 0.61; 1; 1; 1.2;0.65) I want to find 0.6 and 0.65 and not 0.6 and 0.61.

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FV 2020-4-19

I also need to find the index of the values.

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Answer 1

Ameer Hamza 2020-4-19

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编辑：Ameer Hamza 2020-4-20

在 MATLAB Online 中打开

Try this. It also preserve the order of minumum values

A = [0.65;1.2;1.2;0.7;0.6;0.61;1;1;1.2;1];
[vals,idx] = mink(A,3);
if diff(idx(1:2))==1
    I = sort(idx([1 3]));
    min_vals = A(I);
else
    I = sort(idx([1 3]));
    min_vals = A(I);
end

Result:

I =
     1
     5
min_vals =
    0.6500
    0.6000

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FV 2020-4-20

Looks good, How can I get the index of the result?

Ameer Hamza 2020-4-20

See the updated code.

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Answer 2

Mehmed Saad 2020-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/519052-find-two-minimum-values-not-followed-by-each-other#answer_426909

编辑：Mehmed Saad 2020-4-19

在 MATLAB Online 中打开

The long Method

A=[1;1.2;1.2;0.7;0.6;0.61;1;1;1.2;0.65];
miny = [];
for i =1:3
x = min(A);
A(A==x) = [];
    if(i~=2)
        miny = [miny x];
    end
end
miny

The short one

A=[1;1.2;1.2;0.7;0.6;0.61;1;1;1.2;0.65];
B = sort(A);
miny = [B(1) B(3)]

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Image Analyst 2020-4-19

So the long method is too long, but the short method is too short. Exactly how many lines of code do you want?

FV 2020-4-19

I don't want to sort it and therefore the short one doesn't work. I also need it to work for other A's.

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Answer 3

Image Analyst 2020-4-19

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在 MATLAB Online 中打开

Try this:

A=[1;1.2;1.2;0.7;0.6;0.61;1;1;1.2;0.65];
% Plot, just for fun.
plot(A, 'r.-', 'MarkerSize', 30);
grid on;
% Find the values in ascending order, so the min value will be at location/index = 1.
[sortedA, sortOrder] = sort(A, 'Ascend')
% Now find the second lowest value but it can't be in the location next to the lowest value.
% Use diff() to see how many indexes the values are separated by each other by.
d = diff(sortOrder)  % Don't want 1's
% Get min1 and min2 according to the non-consecutive criteria.
min1 = sortedA(1)
if d(1) ~= 1
	% Not consecutive so we're OK.
	min2 = sortedA(2) % Get the next one
else
	% Consecutive so pick the next location with the next lowest value.
	min2 = sortedA(3)
end