MATLAB: How to index elements by their sorted positions

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I have a question regarding indexing vector elements according to their position in a sorted list. The usual query I have seen is more like this, where the secondary output of sort() is sufficient – but not for my purpose.
The problem (using R2019a in Windows 10):
I have a vector (which could be arbitrarily long, with an arbitrary number of sets of replicants, each of which could have an arbitrary number of elements).
A = [20    23     1    19    20     8     5    14     9     7];
and can happily sort it:
>>B = sort(A) 
B =  
     [1     5     7     8     9    14    19    20    20    23]
I want to create another vector C whose ith element describes the index position within B of the ith element of A. Duplicates should be handled by their original appearance order.
i.e., the desired C = [8 10 1 7 9 4 2 6 5 3]
C therefore has the properties: sort(C) = 1:size(A), and size(unique(C)) = size(C).
for ii = 1:size(A,1)
    C(ii) = find(B,A(ii))
end
almost works. It doesn't handle duplicate values though, and returns C(5) = 8 instead of 9. (It's also non-vectorised and therefore presumptively ugly.)
A nastier test selection would be
>>A = [42  23  23   7   9   7   8   1  10  23   9   9   1   2  23  23  16  18   7   9];
>>B = sort(A)
B = 
     [ 1   1   2   7   7   7   8   9   9   9   9  10  16  18  23  23  23  23  23  42];
with corresponding
C = [20  15  16   4   8   5   7   1  12  17   9  10   2   3  18  19  13  14   6  11]
I'd appreciate any ideas on how to handle duplicates – or direction to the appropriate question/answer/function if my GoogleFu isn't up to scratch.

Best Answer

Sort has a second output that is the index;
[B,I] = sort(A);
such that A(I) = B;
From there, I is the C_ matrix you are looking for with non-unique elements shown as well. You can extract the unique element indeces using the [temp,index]=unique(B) function on B to obtain the indeces of B that are unique and equate C = C_(index).
Working Solution;
A = [20    23     1    19    20     8     5    14     9     7];
[B,idx] = sort(A) ;
indA = 1:length(A);
[temp,idB] = sort(idx);
C = indA(idB)
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