Questions tagged [data-structures]
Questions on using or implementing more or less common data structures such as linked lists, structs, trees, tries, heaps etc. in Mathematica.
0
votes
1answer
100 views
How can I translate some JavaScript code into Mathematica code? [on hold]
I am a programmer and would like to understand another field outside of the procedural thinking of if-else and for.
I would ...
10
votes
1answer
389 views
Pascal records and Mathematica programming
Background:
"experienced" Pascal-programmer (DOS-era, never got into OOP)
proud owner of Mathematica ver 11.2
have used Mathematica for years to do my share of number crunching and plotting to ...
13
votes
6answers
228 views
How to invert MapIndexed on a ragged structure? How to construct a tree from rules?
I have an arbitrary ragged nested list-of-lists (a tree) like
A = {{a, b}, {c, d}, {{{e, f, g, h, i}, {j, k, l}}, m}, n};
Its structure is given by the rules
<...
4
votes
2answers
130 views
Converting from “matrix” data into “coordinate” data
Say I have data which looks like data1 - this is "matrix" like data (is there a better descriptor?). The data looks like a matrix, and at each point in the matrix, ...
3
votes
0answers
69 views
Approximate Nearest Neighbors in Mathematica?
Is there any support for Approximate Nearest Neighbors (ANN) in Mathematica or third-party packages? I'm looking for a good implementation of locality sensitive hashing for applications where ...
3
votes
1answer
59 views
What's the best way to import such dataset?
https://www.ocr.org.uk/Images/400305-large-data-set-lds_1-h630-2018-h640-2018-2019-pre-release-data-mei.xlsx
What's the best way to import such dataset?
I have tried to use
...
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 ...
4
votes
1answer
60 views
Local Storage of Periodically Collected Data (without using DataDrop)
I would like to take periodic measurements (e.g. noise levels and temperature in my office from a Raspberry Pi, etc.), say, every minute and have a long-reaching record of this similar to Stephen's ...
9
votes
1answer
471 views
Tree-like data sets with efficient storage and retrieval
Most probably this is going to be a duplicate, sorry. I found too many questions/answers here about tree-like structures, and still could not locate what I want.
It is a followup of my previous ...
13
votes
1answer
253 views
Data re-structuring by Thread
Thread can do this
Thread[{a, {b, c, d}}]
{{a, b}, {a, c}, {a, d}}
But when above ...
5
votes
3answers
178 views
ByteCount on Function
I was comparing RAM and CPU efficiency for List, Rule, Association, Function. The following code
...
3
votes
1answer
81 views
Get the dimensions from the SparseArray properties
In the sparse matrix, we have a list of properties: specified elements, dimension, default, and density. I am interested in getting this data without calculating them again.
For an example, the ...
1
vote
1answer
99 views
SparseArray: accesing nonzero row and column entries
I have an enormous $m\!\times\!n$ sparse matrix $d$ with $l$ nonzero entries, stored as d=SparseArray[{{i1,j1}->w1,...,{il,jl}->wl},{m,n}];.
How do I access ...
0
votes
1answer
55 views
Given a data set, how to do the following
Please help in executing the following problem in Mathematica:
I have the following set:$A=\{1, 2,3,4,5,6,7,8,9,10\}$ (my actual data has more than 10 points). I need to do the following three steps:
...
1
vote
1answer
98 views
Dynamically update of Association
I try dynamically to add new keys and update the values of existing keys in given dataset (Association). I implement this by the following code:
...
0
votes
1answer
48 views
Delete duplicates and sort a list of sets separately? [closed]
I have a set where it has three subsets. I want to have each element of each subsets appears only once, sorted, but the order of subsets does not change. For example: I want to get from
$$
\{\{5,2,2,3\...
1
vote
2answers
109 views
1
vote
0answers
45 views
Create Association from Expression
I have a set of algebraic expressions of a certain form, and I would like to make them into Associations in a specified way. My expressions are formed of two heads, ...
1
vote
3answers
79 views
Simple implementation of a multi-part ratio data structure
A multi-part ratio would be an expression of the form:
$e_1:e_2:e_3:\cdots:e_n$
It would have the following properties:
When the expressions are natural nos, they can be evaluated to be $$\frac{...
3
votes
0answers
72 views
HDF5 does not support string?
I did a simulation for Baccarat.
So some results are saved like this.
...
3
votes
0answers
40 views
Possible to add a “Heading” for the columns in HDF5 format?
A similar post was found here, but it's not using MMA.
A small test to export HDF5 file,
...
0
votes
1answer
49 views
determine the structure of Data in sum of two subsets Modulus $n$
I wrote a code below to determine the cases when two subsets of a set $\mathbb{Z_n}=\{0,1,2,\ldots,n-1\}$ are added together element by element (without removing the multiplicity) in $\mathbb{Z_n}$ ...
5
votes
4answers
414 views
count the pairs in a set of Data
I have a list of Data, e.g.,
list1={0, 1, 1, 1, 1, 2, 2, 3, 3}
list2={0, 1, 1, 1, 1, 2, 2, 3, 3, 0}
and I want to get as an output ...
0
votes
0answers
73 views
How to organize code for simulating many ODEs?
I have a large model with many variables (about a hundred) and many differential equations (non-linear). What is the best way to handle a system this size in Mathematica?
Note that I am not asking ...
5
votes
3answers
189 views
Multi-coloured tree plot
I am trying to create a multi-coloured tree plot (Mathematica 9) where each branch is coloured according to its parent node value. For example, for a tree plot with three nodes, n1, n2 and n3, coming ...
5
votes
2answers
125 views
How to Label only Certain Vertices in a Network Based on Eigenvector Centrality?
Using the Following Network:
footballNetwork = ExampleData[{"NetworkGraph", "AmericanCollegeFootball"}];
Graph[footballNetwork, VertexLabels -> "Name"]
I ...
11
votes
3answers
199 views
Support for low-complexity (compressible) lists
By "low-complexity list" I mean a list like the following:
lcl = {17, 17, 17, 17, 17,
21, 21, 21, 21, 21, 21, 21, 21,
11, 11, 11, 11, 11, 11, 11}
...
2
votes
0answers
55 views
Data structure for finding pairs of matrices under constraint
PROBLEM DESCRIPTION
Given three positive integers k, n1, n2, I have a list of matrices
matrices = Tuples[Range[0,k], {n1,n2}]
...
3
votes
3answers
112 views
Building matrix from relational data
I'm new to Mathematica, coming from Python, and I'm having a hard time trying to build a matrix from relational data.
The data looks like this:
...
7
votes
3answers
175 views
How to disallow the application of functions outside a white list?
In an earlier post I described a special kind of list (actually, a special kind of multiset) that can be represented more efficiently with a structure like this:
...
20
votes
3answers
751 views
How to implement a discrete data representation?
I'm currently working with large datasets of "discrete data". Each of these is a multiset of real numbers of the form $kS + B$, where $k$ is an integer, and $S$ (the "scale") and $B$ (the "bias") are ...
14
votes
1answer
765 views
How to use classical data structure in Mathematica
As a C programmer, I have used Mathematica for a month. In this process, I discovered that some problems cannot be solved via the built-ins, owing to lacking of data structure like ...
26
votes
1answer
701 views
How to use the iterator in Mathematica
I find the Mathematica has the iterator data structure. We can build some iterators like this:
Constant iterator
GeneralUtilities`ConstantIterator[5]
Key ...
3
votes
2answers
377 views
Convert between list of 3D coordinates and 2D array
I have a dataset that I import from a csv file. It's a rectangular array of values, with the first row and first column specifying the x and y coordinates. I want fit this data to a 2D function using <...
6
votes
6answers
164 views
List structure transformation
How to transform a list as
{{x,y},{a,b,c,d,e}}
into the form of
{{x,y,a},{x,y,b},{x,y,c},{x,y,d},{x,y,e}}
elegantly, ...
0
votes
1answer
56 views
How does one create getter methods that depend on a variable (besides its argument)?
In the (as always) insigthful answer by Leonard Shifrin to this MMA SE post
https://mathematica.stackexchange.com/questions/52393/how-to-make-use-of-associations
...
2
votes
0answers
92 views
List, Association, and Dataset, according to what principles to choose which one to use?
List, Association and Dataset are three 'objects' that can be used to store data in MMA. So ...
1
vote
3answers
86 views
Clustering with a certain number of members
Is it possible to find exact number of clusters with exact numbers of members in each cluster?
Something like this:
...
6
votes
2answers
516 views
How to efficiently implement Disjoint Set/Union Find data structure?
The data is a list of lists (sets), where all the elements are distinct. There are basically two operations.
Find the position that contains a certain element. (And fast accessing the set with this ...
5
votes
4answers
739 views
Is *.dat file suitable for storing high (>2) dimensional matrix?
The typical process goes as first one exports a numerical matrix mat
Export["test.dat",mat,"Table"]
and then imports it back ...
4
votes
1answer
155 views
Create tree association using table
Suppose I have a table like the following (This example is simplified, actual table is much larger), it is read from external files:
...
1
vote
0answers
41 views
Looking for a package for data on (sparse) uniform grids
I have large amounts of sparse 2d and 3d "volumetric" data, i.e. fixed data associated with positions in a uniform (integer coordinate) grid. I think of it as partial function
$$f: \mathbb Z^n \to D.$...
0
votes
0answers
49 views
Data structures in mathematica for choosing permutations
I am trying to classify permutations of n, in this case n=6, elements depending on the cycles that contian the points 1 and 2, since these are considered to be special points.
So for example, I will ...
3
votes
1answer
90 views
Dealing with a large number of optimizations performed with parameters read in from a CSV file
I have a large CSV file (1.5M rows), with each row containing a set of parameters that I need for an optimization routine in Mathematica. I'm hoping to import the data, run the computation, and then ...
0
votes
1answer
74 views
Manipulation of imported Datafile
Since I am solving a differential equation in a for loop with NDSolve
...
2
votes
0answers
76 views
How to implement shared data structures?
If I have a shared data structure like you would find in nested C structs, how would I best implement that in Mathematica?
I have some "object-oriented" code I would like to port to Mathematica. It's ...
7
votes
1answer
61 views
KaryTree of Text .csv and Correlation
How can I make a KaryTree of this raw-data (raw-data at the end of the question):
This is is data from a political survey in which I ask 5 questions with the following possible answers:
Q1: 'Y'= Yes,...
2
votes
0answers
55 views
How to use a picture to store some data [duplicate]
As we know.The values of the types is "Real" defaultly in Mathematica.In the Image documentation's detail we can see
Image[...
4
votes
1answer
263 views
Immutability, Association and typing
I have read the article by Leonid on the question. I am still struggling.
I am trying to use Association to inject some pseudo-typing in my code.
Here is my ...
0
votes
0answers
27 views
Mapping Functions to Associations [duplicate]
If I have the association matrix listed bellow and I want to apply:
...
