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Results tagged with associations
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user 4999
Questions on the associative data-structure introduced in Mathematica version 10.
5
votes
Replace Missing[Unmatched] with zero
A couple of alternatives:
assoc = <|"key" -> "2009-ABCDE", "ActuarialEPI" -> 26603.6,
"ReportedEP" -> 28535., "ReportedLI" -> 0., "ELI" -> 25619.3,
"DLI" -> 25619.3, "EstimatesEP" -> Missing[ …
- 245k
3
votes
Accepted
How do I thread an Association?
Something like this?
network[n_List] :=
MapThread[
(<|"w" -> Table[RandomVariate[NormalDistribution[]], #2, #1],
"b" -> Table[RandomVariate[NormalDistribution[]], #2]|> &),
{Most@n, R …
- 245k
5
votes
Accepted
Unexpected behavior with Derivative and a function parameters defined via an Association
Why is the result
Missing["KeyAbsent", 2] + Derivative[1][z[2]][y]
Heads are evaluated first. The head of Derivative[0, 0, 1][func][x, 2, y] is Derivative[0, 0, 1][func], which yields the followin …
- 245k
5
votes
Accepted
Why AssociateTo does not work when Association is inside a list?
Further, I think a complete example would exhibit what happens to the source associations ode1 etc., namely that ODEs is changed but not ode1. … If you prefer working strictly with associations, you could modify the definition of setupDiffEq or add a definition like setupDiffEq[a_?AssociationQ] := setupDiffEq@Normal@a. …
- 245k
3
votes
How to swap keys and values of an association?
I suppose AssociationThread[Values@assoc, Keys@assoc], but it's not invertible if the values are not distinct.
Also Association@KeyValueMap[#2 -> #1 &, assoc] with the same caveat.
- 245k
9
votes
How to make arbitrary transpositions of associations and datasets
If you factor a permuation perm into a product of cycles of the form $(j\ k)$ with $k=j+1$, then the permuation can be effected by Query and Transpose.
Functions:
adjacentCycles[perm] (* factors per …
- 245k
7
votes
Reverse Lookup: getting keys from values
There's a certain elegance to:
GroupBy[assoc, Identity, Keys] (* gives all keys for a given value *)
GroupBy[assoc, Identity, First@*Keys] (* gives first key for a given value *)
GroupBy[as …
- 245k
10
votes
Pattern matching Association in rules
One way to fix the OP's problem is to evaluate the associations in the patterns:
Cases[assocRuleList, HoldPattern[<||> :> _ // Evaluate]]
(* {<||> :> "zero"} *)
Cases[assocRuleList, HoldPattern[<|" …
- 245k
11
votes
Accepted
Apply a function row- and columnwise
If we change dt to:
dt = Dataset@<|
"Arizona" -> <|"1801" -> 60, "1802" -> 1530, "1803" -> 100,
"1804" -> 665|>,
"Kansas" -> <|"1801" -> 1160, "1802" -> 415, "1803" -> 825,
"180 …
- 245k
4
votes
Accepted
Average length (in words) of paragraphs in document
How picky are you about what counts as a word?:
ExampleData[{"Text", "PrideAndPrejudice"}];
assoc = Association@MapIndexed[First@#2 -> # &, StringSplit[%, "."]];
WordCount /@ assoc // Total // Absol …
- 245k
6
votes
List[...] + Association[...], or Association[...] + List[...], when does the order matter?
It's probably a bug related to packed arrays:
<|"a" -> 10, "b" -> 10, "c" -> 10|> + Developer`ToPackedArray[{1, 2}]
(* {<|"a" -> 11, "b" -> 11, "c" -> 11|>, <|"a" -> 12, "b" -> 12, "c" -> 12|>} *)
…
- 245k
4
votes
Accepted
How to map or import list of lists as associative array (dictionary)
Like this?
AssociationThread @@ Transpose@data
(* <|"7A37D069" -> "Copper", "6D2C07C7" -> "Autograph"|> *)
The data in the comment below can be made into an Association as follows:
Association …
- 245k