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Questions tagged [associations]

Questions on the associative data-structure introduced in Mathematica version 10.

0
votes
2answers
61 views

Association on a list

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
202 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
60 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
32 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
101 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
549 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
224 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
49 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
152 views

Picking/Selecting in an association

suppose I have 2 associations t1=<|"a" -> 1, "b" -> 2, "c" -> 3, "d" -> 4|> and ...
5
votes
1answer
92 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
41 views

Ranking polynomials based on global maxima

Suppose I have the following polynomials in an association i.e. <|...|>, they are: ...
0
votes
4answers
122 views
5
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2answers
91 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
187 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
111 views

Delete zeros from a sparse array [duplicate]

Why doesn't SparseArray automatically remove zero entries? The code ...
6
votes
0answers
53 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
308 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
179 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
85 views

Merge Associations and replace absent value with 0

I have two associations like this ...
3
votes
1answer
44 views

KeySelect via Not[StringMatchQ[Pattern]] fails

I have an Association asc that has mixed type Keys: ...
0
votes
1answer
118 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
62 views

unexpected result from augmented assignment to association

Is the last of these results expected? If so, how? ...
10
votes
1answer
89 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
208 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
89 views

speedy update of list of associations

Suppose as is a list of associations that I want to update. For example: ...
12
votes
3answers
277 views

Convert List of Associations into Association of Lists

For neural networks mathematica likes 2 ways to structure training sets: ...
3
votes
2answers
128 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
97 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
62 views

Filter rows in nested Association / Dataset using Select

The Dataset I am working with has the following nested structure. ...
1
vote
1answer
79 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? ...
6
votes
2answers
113 views

How to use ReplaceAll and RuleDelayed with an Association? [duplicate]

I expected that something like this ...
6
votes
1answer
84 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
210 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
241 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
178 views

ByteCount on Function

I was comparing RAM and CPU efficiency for List, Rule, Association, Function. The following code ...
1
vote
1answer
127 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
120 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
35 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
127 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
68 views

List of Strings to Associations [closed]

I have a list of Strings, some thing like below: ...
6
votes
1answer
89 views

How to update values of particular keys efficiently

Say I have a list of Association, SeedRandom[45] test = Association[Table[i -> RandomInteger[30], {i, 6}]] <|1 -> 18, ...
1
vote
1answer
44 views

How to draw DensityPlot on a given association? [closed]

I want to draw a DensityPlot similar to below:- DensityPlot[Sin[x] Sin[y], {x, -4, 4}, {y, -3, 3}] But my problem is, I am not given the function itself. I am ...
5
votes
1answer
107 views

Replace value in association data-set

I have an association dataset with a depth of two (each value is an association too, and the size of the dataset ~ 30000 keys and an average size of values are ~2000 keys association). The dataset ...
1
vote
1answer
48 views

Selecting nonzero rules from a list

I have a list of rules: list = {a1 -> 0, a2 -> 3x, a4 -> 0, a5 -> 5x+3...}. I would like to append to another list the nonzero rules, which are: ...
1
vote
1answer
35 views

Get values of Dataset in depth 2

Given the following dataset ...
3
votes
1answer
70 views

A calculation in two depth association

I have a dataset where values are associations too. ...
1
vote
1answer
77 views

Why do I need a second Function in SortBy for Association?

I cannot understand why I need a second pure function when trying to sort Association by Key. Here is an example ...
3
votes
1answer
111 views

Associations & generating training sets

Solution: Pi is allowed in training sets, but not in batches generated by the batch generating function preamble: I want to generate my own batches of training data for training a deep CNN. ref/...