Questions tagged [associations]
Questions on the associative data-structure introduced in Mathematica version 10.
1
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2answers
59 views
How to use KeyValuePattern with individual replacement rules?
What's the syntax to use individual replacement rules for key-value patterns?
This returns only the first match:
...
4
votes
4answers
116 views
Neat redistribution of association values
Given an original association:
original = <| "a" -> {a1, a2}, "b" -> {b1, b2}, "c" -> {c1, c2} |>
and a set of redistribution rules e.g.
<...
1
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2answers
59 views
2
votes
1answer
31 views
Hierarchically adding {…keys..}->value to an association
Given a list of keys {"a","b","c"} and a value 3 (associated to the last key) I want to define a function that is equivalent to ...
3
votes
0answers
62 views
Get Windows registry into Mathematica as an association
Windows probably is the only operating system that has a separate database of configuration instructions and paths. The windows registry looks exactly like a giant nested association. Also probably is ...
4
votes
1answer
59 views
Inconsistency in getting Keys, Values and Query for nested Rules
Querying nested Rule expressions of the form
a -> v -> b // FullForm
Rule[a,Rule[v,b]]
for ...
2
votes
1answer
44 views
Turns nested Lists into nested Associations, ReplaceAll for list vs ReplacsAll for association
I want to transform some nested lists into nested associations except the "rows"->List pattern.
Here is the example
...
1
vote
1answer
52 views
Sorting each column in a nested list contained in an association
I have an Association which contains three arrays 200x1000x2.
Each row m of a matrix denotes a different set of parameters, while
each column n contains the outcomes of the function for a specific ...
0
votes
2answers
65 views
Association on a list [closed]
I have a dataset under this form :
sentence = {sentence1, sentence2, sentence3,...}
and a list of label :
label = {1,2,3,4,5,6,7...} both have same length !
So I want to make an association ...
4
votes
1answer
207 views
Inexact numbers as keys in Association?
Can someone explain me how Mathematica's Associations behave with inexact numbers as keys:
<| 0.22499999999999964` -> a |> [0.22499999999999965`]
and
<...
3
votes
1answer
64 views
Reducing boilerplate with associations
I'm looking for advice either on alternative ways to approach my problem in general, or specifically on meta-programming (which seems to me to be a way around this). In my work I have databases of ...
1
vote
0answers
37 views
How do I Select when the key of an association is a multi-word string [closed]
I have imported some survey responses into a Dataset. I now want to select those rows where the response to "participant type" == "Virtual". I discovered that this ...
2
votes
1answer
106 views
Deleting missing values from a dataset
I wanted to create a dataset of all UFO sightings in April of 2018. The
AssociationThread doesn't want to work, because some of the entries are missing value, what ...
19
votes
4answers
556 views
Is it possible to avoid unpacking when merging Association?
For example, if we have
assoc =
AssociationThread[{1, 2, 3} -> RandomReal[1., {3, 10}]];
and
...
7
votes
3answers
225 views
Obtaining a matrix of complex values from associations giving the real and imaginary parts of each element?
I have a list of associations keyed by real and imaginary numbers, like so:
...
2
votes
1answer
53 views
Converting an expression with strings to an association
I have an expression which contains a bunch of strings and some complex valued numeric factors in front. A couple of summands might look like this:
...
4
votes
2answers
157 views
Picking/Selecting in an association
suppose I have 2 associations
t1=<|"a" -> 1, "b" -> 2, "c" -> 3, "d" -> 4|>
and
...
5
votes
1answer
97 views
Define an access by key ( structure[key] ) for a custom structure struct?
I have some "complicated" data that I want to encapsulate into a "struct":
For instance (imagine that data have several fields):
...
7
votes
5answers
326 views
Unexpected behaviour of Nothing inside List inside Association
When evaluating the following input:
<|a -> {c, d, e}|> /. d -> Nothing
I get (expression 1):
...
3
votes
1answer
42 views
Ranking polynomials based on global maxima
Suppose I have the following polynomials in an association i.e. <|...|>, they are:
...
0
votes
4answers
136 views
5
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2answers
98 views
How to prevent arguments UpValues from being used in selective functions
Ok, I know the simple answer is to set some form of Hold attribute to the function but bear with me for a bit while I explain my motivation and why that is not quite what I want.
I have a collection ...
1
vote
1answer
201 views
Bottom-most left-most entries in a sparse array
I have a list bdrs of SparseArrays, which represent the boundary matrices of a chain complex $R^{d_0}\overset{\partial_1}{\...
4
votes
1answer
127 views
Delete zeros from a sparse array [duplicate]
Why doesn't SparseArray automatically remove zero entries? The code
...
7
votes
0answers
61 views
Substitute for Association inside Compile?
Associations are not compilable, so I’m looking for a workaround to this. That is, I need a mutable hashtable-like data structure with fast key value lookups ...
10
votes
3answers
314 views
Min and Max of a list of Associations
I am trying to find the minimum values for all elements in a list of associations, below is an example
...
3
votes
2answers
201 views
Iterate over keys of association
How do you iterate over the keys or rules of an association (in any order)? E.g. for
<|"0"->"a", "1"->"b", "2"->"c"|>
I would like to either ...
2
votes
3answers
89 views
3
votes
1answer
46 views
KeySelect via Not[StringMatchQ[Pattern]] fails
I have an Association asc that has mixed type Keys:
...
0
votes
1answer
127 views
Aggregate function problem
I use a function to do something similar to a SQL sum. I've asked about simplifying it in another post. I'm still using this function and it works well for aggregates like ...
6
votes
1answer
64 views
unexpected result from augmented assignment to association
Is the last of these results expected? If so, how?
...
10
votes
1answer
98 views
Parallelize[MapIndexed[…,Association[…]]] returns broken result
Bug introduced in 10.0.2 or earlier and persisting through 12.0
Confirmed: CASE:4041910
Consider the following example:
...
5
votes
1answer
222 views
Parallelize the construction of sparse matrices
I'm trying to parallelize a few constructions of chain complexes (given as a list of sparse matrices). I have a function that for any column (or row) computes the list of nonzero entries in that ...
1
vote
0answers
39 views
Extracting Parts of Speech
I am looking to parse the ConstituentsTree from TextStructure.
Someone already asked how to get the proper nouns out of a text here:
Extract names from a document
I am looking for a more general ...
4
votes
2answers
91 views
speedy update of list of associations
Suppose as is a list of associations that I want to update.
For example:
...
12
votes
3answers
298 views
Convert List of Associations into Association of Lists
For neural networks mathematica likes 2 ways to structure training sets:
...
3
votes
2answers
131 views
Merge associations with the same keys, same in a sense by user's definition
I know that it is the standard functionality of Merge to combine the values of the same keys among associations.
Now I would like to deal with a situation in which,...
6
votes
2answers
101 views
GraphDistance error when Graph vertices are Associations
Bug introduced in 10.0 or earlier and fixed in 12.0
Note: Associations are new in 10.0
Here is a nice graph whose vertices are Associations:
...
2
votes
1answer
70 views
Filter rows in nested Association / Dataset using Select
The Dataset I am working with has the following nested structure.
...
1
vote
1answer
85 views
Converting a list of associations into a single association
How do i smartly join a List of Associations (eg. returned by ParallelTable) such that i get a single Association?
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6
votes
2answers
121 views
How to use ReplaceAll and RuleDelayed with an Association? [duplicate]
I expected that something like this
...
6
votes
1answer
88 views
How can I update an association with a function?
I'm not sure if this is a bug, or if I just am not understanding, properly, how to create a function.
I am able to use a list of rules to update an association like so:
...
7
votes
2answers
211 views
How can I map associations to expressions?
I have a list of associations, and I would like to make it so that an expression automatically reads the associated data from the associations list, that has the same name, into the expression. An ...
8
votes
2answers
245 views
Deleting all keys that have null values
I have a notebook that I am working on that starts with an imported CSV file. Many of the rows have blank data in them. I have used the following command to establish a list of associations:
...
5
votes
3answers
179 views
ByteCount on Function
I was comparing RAM and CPU efficiency for List, Rule, Association, Function. The following code
...
1
vote
1answer
129 views
How to make an Association of Assocations [closed]
As a learning exercise I’m trying to convert some data we have from spreadsheets into an association of associations. However, I’ve only managed to format two different associations, a key of the ...
11
votes
1answer
123 views
stable sort for association?
Should I be able to use the "list of functions" approach to getting a stable sort of an association? In 11.1 I see,
...
0
votes
1answer
44 views
how to get association from json? [closed]
How do I convert {{"a" : 13, "z" : 24},{"f" : 17, "h" : 94}} to get
{{"a" -> 13, "z" -> 24},{"f" -> 17, "h" -> 94}}
I am trying to change : to ->
3
votes
3answers
129 views
Simpler way to thread dataset values to each other
I have a relatively simple dataset that provides a list of values for a list of countries:
...
0
votes
1answer
72 views
