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query - Unix-like reference to parent and root Association?


Is there a syntax or function to reference parent and root when querying nested Associations similar to Unix' ".." and "/", eg "cd ../../mydir". ?


Here's a typical application of the root construct. Given a nested dataset:


ds = <|  "study" -> <|   "all"  -> <|"n" -> 223.`, "Median" -> 18.5` |>|>, 
        "bySite" -> <|   "VASD" -> <|"n" -> 107.`, "Median" -> 20.40`|>, 
                         "UCSD" -> <|"n" -> 116.`, "Median" -> 16.5` |>|>, 
  "bySpeciality" -> <|"Primary" -> <|"n" -> 127.`, "Median" -> 17.8` |>, 

                    "Specialty" -> <|"n" -> 96.` , "Median" -> 19.5` |>|>|> // Dataset

enter image description here


(Dataset is only used here for formatting convenience)


using ds["study","all","n"] as denominator, the query is to convert all values of the instances "n" to ratios:


   ds[All, All, #/ds["study", "all", "n"] &]

enter image description here


But how can it be used in a query without reference to ds? For example, would like to use something like RootAssociation


ds // Query[All, All, {"n" -> (#/RootAssociation["study", "all", "n"] &)}]


ParentAssociation would work in a similar way




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