Sort elements of an array with a given a priority, keeping track of indexes (includes repeated elements)

Hi,

I would like to sort an array vR = [1.5 2 1.25 3 3.5 5 8 2.359 3] with the following rules:

1. Sorted integers
2. Sorted half integers
3. Sorted quarter integers
4. Remaining sorted elements

After the sort is completed, I want to know the indexes of elements in the new array relative to the previous unsorted array.

Note: there can be repeated elements

vR_sorted = [2 3 3 5 8 1.5 3.5 1.25 2.359]
idxs = [2 4 9 6 7 1 5 3 8]

Thanks

Answer 1

[Stephen23]

>> vR = [1.5,2,1.25,3,3.5,5,8,2.359,3]
vR =

   1.5000   2.0000   1.2500   3.0000   3.5000   5.0000   8.0000   2.3590   3.0000

>> [~,idx] = sortrows([bsxfun(@mod,vR(:),[1,0.5,0.25])~=0,vR(:)])
idx =

   2
   4
   9
   6
   7
   1
   5
   3
   8

>> vS = vR(idx)
vS =

   2.0000   3.0000   3.0000   5.0000   8.0000   1.5000   3.5000   1.2500   2.3590

For MATLAB versions R2016b and later bsxfun is not required:

[~,idx] = sortrows([mod(vR(:),[1,0.5,0.25])~=0,vR(:)])

Answer 2

[Kevin Phung]

There might be something more elegant than my for-loop, but this should work. Let me know!

vR = [1.5 2 1.25 3 3.5 5 8 2.359 3 ];
integers = vR(floor(vR) ==vR); % rule 1
a = vR(not(ismember(vR,integers))); %NOT integers
half_int = a(floor(a - .5) == a-.5); %half integers
b = a(not(ismember(a,half_int))); % NOT half integers

list1 = b(floor(b - .25) == b-.25);
list2 = b(floor(b-.75) == b-.75);
quarter_int = [list1 list2];

leftOvr = b(not(ismember(b,quarter_int))); % remaining

sorted_vR = [sort(integers) sort(half_int) sort(quarter_int) leftOvr];
idx =[];
for i = 1 :numel(vR)
    if any(ismember(vR,sorted_vR(i)))
        idx1 = find(ismember(vR,sorted_vR(i)));
        idx = [idx idx1]; % this will add in duplicates
    end
end
idx = unique(idx,'stable'); % remove duplicate indices