Sorting a vector by the number of times each value occurs

Question

The following case takes place:

Q = [idxcell{:,1}]; Sort = sort(Q,'descend') Sort = Columns 1 through 13 23 23 22 22 20 19 18 18 18 18 17 17 17 Columns 14 through 26 15 15 14 14 13 13 13 12 12 12 11 10 9 Columns 27 through 39 9 9 8 8 8 8 8 7 7 7 7 7 7 Columns 40 through 52 7 6 6 6 5 4 4 3 3 3 3 2 2 Columns 53 through 64 2 2 2 2 2 2 2 1 1 1 1 1 

How can we sort the Sort matrix depending on how many times its values ​​are repeated?

The expected result should be:

 repeatedSort = 2(9) 7(7) 1(5) 8(5) 3(4) 18(4) 6(3) 9(3) 12(3) 13(3) 17(3) 4(2) 14(2) 15(2) 22(2) 23(2) 5(1) 10(1) 11(1) 19(1) 20(1) or repeatedSort = 2 7 1 8 3 18 6 9 12 13 17 4 14 15 22 23 5 10 11 19 20 

Thanks in advance.

Answer 1

Here is one way to do this:

 d = randi(10,1,30); %Some fake data n = histc(d,1:10); [y,ii] = sort(n,'descend'); disp(ii) % ii is now sorted according to frequency 

Answer 2

You can use the TABULATE function from the statistics toolbar, then call SORTROWS to sort by frequency.

Example:

 x = randi(10, [20 1]); %# random values t = tabulate(x); %# unique values and counts t = t(find(t(:,2)),1:2); %# get rid of entries with zero count t = sortrows(t, -2) %# sort according to frequency 

result, where the first column are unique values, the second is their score:

 t = 2 4 %# value 2 appeared four times 5 4 %# etc... 1 3 8 3 7 2 9 2 4 1 6 1