How do I pick a minimum that is not the first value in a matrix with multiple minima?

Hi everyone.

I have a two column matrix M where the first column is a vertor/cell containing five elements x1, x2, x3, x4, x5 and the second column is a number. Many combinations of the x's in the first have the same correspoding number in the second column. I want to pick the minimum number in the second column with the corresponding cell in the first column that has the highest x3 and x5 out all available combinations. I used

 [~, ind] = min([M{:,2}]);
    P(j,:) = M(ind,:);
%Here I store the minimum and the corresponding cell in matrix P

but it picks the first minimum. I do not want just the minimum but the minimum highest x3 and x5. How do I do this?

[Azzi Abdelmalek]

Can you give a short example? and post the expected result

[Image Analyst]

Is M a cell array or an array of integers or doubles? You seem to be mixing them up. Give some code that will create a sample M for us. Make it easy for us to help you, not hard.

[Walter Roberson]

What if the condition is not met? For example in one x3 = 7, x5 = 2, and in another x3 = 4, x5 = 6. Then the second one has the highest x5 but the first one has the highest x3 and no combination has the highest of both.

[Oladunjoye]

Thanks all.

M is obtained from an iteration and it's actually a 26604x2 matrix. Below is an example of what matrix M looks like for a single iteration say j=0.

The column is a vector and the second column is a number.

[0;0;0;0;0] -4

[0;0;1;1;0] -4

[0;2;0;1;1] -4

[0;0;0;0;1] -2

[1;2;1;3;1] -2

[0;0;2;-2;3] -4 (preferred)

[1;-1;0;0;3] -4

[1;1;1;0;2] -4

The one marked preferred is the minimum I want out of all the minimum values but my code

 [~, ind] = min([M{:,2}]);
    P(j,:) = M(ind,:);

will return the first one (i.e [0;0;0;0;0] -4).

How do I make MATLAB return the preferred row?

[Walter Roberson]

I still do not see any reason why there is always going to be a case in which both x3 and x5 are largest, no reason why it is not possible that in one case x3 is largest but x5 is not largest.

[Oladunjoye]

Dear Walter Robertson,

Thanks a lot.

My main the problem is that the code returns the row of the first minimum it comes across,

[0;0;0;0;0] -4,

in this case.

My desired result is that the minimum in the second column should have a corresponding vector in the first column with the x's having values x1= -x2, x3 = -x4 and x5 > 0 just as in the example above.

How do I do this?

Answer 1

[Sajid Khan]

2 6

[4,5] 3

[1,8,7] 8

[3,5,8,7] 2

[3,5,6,9,11] 9 if M is the cell posted above. the the step

 [~, ind] = min([M{:,2}]);

will return ind = 4. Which is correct in my case. But I guess you have to replace your second step by the following one

P = M(ind,1);

Because the cell elements that corresponds to minimum second column element lies in the first column, so it isn't good to search it in whole array by typing

P = M(ind,:);

If you don't want the result to be in form of a cell, then use the following syntax to convert it into a matrix

N = cell2mat(P).

If you have further questions, then you are most welcome to ask.

[Oladunjoye]

Dear Sajid Khan,

Thank you.

I have tried the code above but it did not give the desired result. I have given further details below.

M is obtained from an iteration and it's actually a 26604x2 matrix. Below is an example of what matrix M looks like for a single iteration say j=0.

The column is a vector and the second column is a number.

[0;0;0;0;0] -4

[0;0;1;1;0] -4

[0;2;0;1;1] -4

[0;0;0;0;1] -2

[1;2;1;3;1] -2

[0;0;2;-2;3] -4 (preferred)

[1;-1;0;0;3] -4

[1;1;1;0;2] -4

The one marked preferred is the minimum I want out of all the minimum value.

How do I do this?