OrderingBy

OrderingBy[list,f] gives the positions in list at which each successive element of SortBy[list,f] appears.

OrderingBy[list,f,n] gives the positions in list at which the first n elements of SortBy[list,f] appear.

OrderingBy[list,f,-n] gives the positions of the last n elements of SortBy[list,f].

OrderingBy[list,f,n,p] gives positions in list of elements of SortBy[list,f,p].

OrderingBy[f] represents an operator form of OrderingBy that can be applied to an expression.

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