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11h
comment GroupBy several keys while keeping the Dataset as a Table (List of Associations)
... <| "a" -> 1, "b" -> 2 |>. This is what Apply is good for: change the head Rule (i.e. ->) into something else. What we need here is to change it to Join. Apply[Join][...] is equivalent to Apply[Join, ...] so we can use the form Apply[Join]. I hope this clears it up a bit. Regarding this method, while it works, it's probably not efficient and I am not really happy with it. I find it too convoluted. I am hoping for something simpler ... I'm not yet experienced with Dataset, and even though my answer got accepted, I'm not too confident about it.
11h
comment GroupBy several keys while keeping the Dataset as a Table (List of Associations)
@MitchellKaplan This dataset contains an association, the keys of which are also associations. Normal will convert this outer association, which has the form <| <|...|> -> <| "Sales" -> 1 |>, <|...|> -> <| "Sales" -> 2 |>, ... |> to a simple list of rules, { <|...|> -> <| "Sales" -> 1 |>, <|...|> -> <| "Sales" -> 2 |>, ... }. You can see e.g. the first element of this list using ...[Normal][1]. Now what we want to do is join the left-hand-side of -> together with its right-hand-side into a single association. Instead of having <| "a" -> 1 |> -> <| "b" -> 2 |> we want ...
12h
revised Will Version 9 functions all work in Version 10?
edited body
15h
revised InstallR on OS X with external R installation
edited body
17h
answered Installing R packages using RLink on Mac OS X
18h
awarded  Enlightened
18h
awarded  Nice Answer
1d
awarded  Nice Answer
1d
revised Proving the hairy ball theorem using xAct
added 36 characters in body
1d
comment Retrieve style definitions
@kguler Yes, it is a duplicate, you can vote to close. Thanks for the link!
1d
asked Retrieve style definitions
1d
revised Package function not called from button in a DockedCell expression
added 106 characters in body
1d
revised Package function not called from button in a DockedCell expression
added 193 characters in body
1d
answered Package function not called from button in a DockedCell expression
1d
comment Package function not called from button in a DockedCell expression
If you change the action to Print[DownValues[DuplicateNotebook]], it strangely prints {}.
2d
comment Trial version 10 vs Version 10 Prerelease 13
I tried to write a general answer that will be useful to more people with similar problems. I hope it will solve the problem you see as well.
2d
answered Trial version 10 vs Version 10 Prerelease 13
2d
comment Trial version 10 vs Version 10 Prerelease 13
Close Mathematica, then hold down Shift-Control while starting it again. Did it fix the problem? (Reference)
2d
comment OpenCL vs. CUDA with Mathematica
This is a useful read. In Mathematica, CUDALink has more useful functions that OpenCLLink. Both the CUDALink and the OpenCLLink demos work fine for me on a 2012 MacBook Pro, but I didn't go deep into the technologies. I think using them from Mathematica will be quite similar.
2d
revised Does Dataset round?
edited tags