Sort array based on struct fields' values

Hi all,

I'm having trubles with a specific operation: I'm trying to sort an array that contains four different numbers using a specific struct that associates to each of these number a specific value. For example I have that:

• emitters = [12, 24, 48, 84];
• Frequency.(strcat('Em_',num2str(emitters(idx_em)))) = frequency values associated to that specific emitter

I would like to sort the emitters array (row vector) in an increasing order based on the values indicated in the corresponding struct. So ordering the values in the struct in an increasing order will give an indication of how the array should be organized, and then order the latter as well.

How it can be done?

Thank you for the precious help!

[Stephen23]

"How it can be done?"

SORT the vales from the structure, getting the 2nd output (the sort indices). Use the sort indices to rearrange the vector.

What have you tried so far?

Note that hiding meta-data in fieldnames is complicated and likely makes this task harder. Using e.g. a non-scalar structure instead would likely make this task easier and more efficient.

Answer 1

[Rahul]

According to the information shared, I believe you want to sort the array with respect to the Frequncy attributes associated with each element of emitters array.

Once the frequencies of all the elements in the emitters array is set according to this code:

Frequency.(strcat('Em_',num2str(emitters(idx_em)))) = frequency values associated to that specific emitter

Now by creating a cell array for emitter-frequency pairs,

pairs = cell(length(emitters), 2);
for i = 1:length(emitters)
    emitter = emitters(i);
    pairs{i, 1} = emitter;
    pairs{i, 2} = Frequency.(strcat('Em_', num2str(emitter)));
end

Now, the pairs can be sorted based on frequncy values like,

sortedPairs = sortrows(pairs, 2);

We can extract the array of sorted emitters from the pairs like,

sortedEmitters = cell2mat(sortedPairs(:, 1));

disp(sortedEmitters);

This gives you a list of sorted emitters according to their frequency values.

[slow_hand]

Thank you Rahul, very well defined answer!

Answer 2

[Parag Jhunjhunwala]

Hi Matteo Valentini,

The following is a sample code to sort the array arr1 and rearrange the elements at corresponding indices of arr2:

arr1=[7 8 5 6];
arr2=[1 2 3 4];
[~,sort_idx] = sort(arr1);
arr2=arr2(sort_idx)

arr2 = 1×4

3 4 1 2

[slow_hand]

Thank you Parag, your answer is very well structured as well!