How to find min and max of a matrix?

Hi,

Suppose I have a matrix with two columns:

A= [1.6700 0.5300; 1.6800 0.5400; 1.6900 0.5200; 1.6500 0.5100; 1.7000 0.5500];

And I'm looking for the row which simulaneously gives me the smallest value of the first column and the largest value of the second column, how would I go about doing that?

I'm not looking for the min of the first column and the max of the second column separately. I'm looking for the "best combination", i.e. the single row which gives me the smallest possible value of the first column and the largest possible column of the second column.

Any ideas?

Answer 1

[Steven Lord]

Use sortrows. Specify that you want to sort the first column in ascending order and the second in descending order.

[Kerstin Olsson]

Hi,

Thanks for you reply!

Unfortunatelly, I don't think this solves my problem. For instance, if I try sortrows(A,[1 2],{'ascend' 'descend'}), then I will get the smallest value for the first column. And then, if there are repeated values in the first column, the rows will be sorted based on the second column.

This is not what I'm looking for, since rows are not sorted to find the best combination of the smallest and the biggest values, only on finding the smallest values in the first column.

[Steven Lord]

>> rng(1, 'twister');
>> A = randi(10, [20 2]);
>> B = sortrows(A, [1 2], {'ascend', 'descend'})

The first column of the first row of B has the smallest value among all values in the first column of A. Of all the rows in A that have that value in the first column, the second element in the first row of B has the largest value in the second column of that subset of rows in A.

If that's not what you meant by "best combination" please clarify exactly what criteria you're using to define "best."

[Kerstin Olsson]

To get the best combiation I decided to rewrite the smallest and largets values as deviations from a set target for each. Then I summed those deviations and sorted the sum to find the smallest value.