# Tagged Questions

Questions on using or implementing more or less common data structures such as linked lists, structs, trees, tries, heaps etc. in Mathematica.

3answers
3k views

### What is a Mathematica packed array?

A simple sounding question with a few sub questions: What is the difference between unpacked vs packed array? Are packed arrays more space efficent, how much so? Are packed arrays more time ...
0answers
38 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 ...
1answer
70 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 ...
1answer
55 views

### Manipulation of imported Datafile

Since I am solving a differential equation in a for loop with NDSolve ...
2answers
809 views

### Efficient priority queues?

I'm trying to figure out how to transfer the concept of a priority queue to the functional world. Searches have turned up some implementations that use Append and other expense list copying techniques....
0answers
41 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 ...
1answer
51 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'= ...
3answers
3k views

### How can I add a column into a existing Dataset?

I'm very excited about the brand new Dataset function. I have played with it in Wolfram Cloud, and haven't figured out how can I add a new column into an existing <...
0answers
46 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[...
1answer
108 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 ...
2answers
64 views

### Creating Association [duplicate]

I have provided a dataset bellow and I would like to store the data as an Association that I can query. Such that e.g. ...
0answers
23 views

### Mapping Functions to Associations [duplicate]

If I have the association matrix listed bellow and I want to apply: ...
2answers
262 views

### Is there a method to enumerate the keys/values of SystemUtilitiesHashTable

Lacking from the simple API of SystemUtilitiesHashTable is a method to enumerate the keys/values. ...
3answers
6k views

### How to make use of Associations?

I have been curious about it for long. Now that Mathematica 10 arrives, I think it's time to ask the question: How the new Association data structure would be used ...
2answers
85 views

### Merge two trees into a rectangular matrix in Mathematica

How can I merge two trees, t and s, so as to form a square matrix below, where both trees starts from top-left (as shown), and ...
7answers
272 views

### Extract left-upper triangular data from a square matrix-form list

Hopefully, this question is not too basic or obscure. I'd like an idea on how to extract this {{1}, {5, 2}, {9, 6, 3}, {13, 10, 7, 4}} from ...
0answers
53 views

### How to transform a tree-form list to matrix-form list in Mathematica? [closed]

Excuse my naive question. Is there a quick/efficient way to transform {{1}, {1, 2}, {1, 2, 3}, {1, 2, 3, 4}} to a lower-triangular matrix-form ...
1answer
117 views

### Fitting multiple peaks

I am using the code found here to fit multiple peaks of a large dataset which I don't know anything about. This was the only code I could find on the internet to do such a thing. So this is my attempt ...
3answers
5k views

### Implementing a dictionary data structure

As one learns from a course on data structures, hash maps or dictionaries can be efficient when applied to appropriate tasks. I need a hash map in Mathematica and I've never found it. I'm scratching ...
1answer
170 views

### How to fit multiple Gaussian peaks to data [duplicate]

How would I fit this data with Gaussian Peaks? I have tried various codes but none have even worked. Note: If I do Log[data], the peaks are more visible (I have tried the method from here but it got ...
0answers
21 views

### Remove background from multipeak data [duplicate]

Let's say I have a a very large list of data in the format {{n,f[n]}} so something like {{1,600},{2,700},{3,1100}...} and if this data is plotted, then it will look like a sum of Gaussian functions+a ...
0answers
34 views

### Repeat code segment from certain cell [closed]

If I have a lot of code and wish to repeat it in a different cell, but with some variables changed, how do I do it? (without copying and pasting) I tried using GoTo and Label but it did not recognize ...
1answer
148 views

### Resampling Data using Temporal Data

I am having a problem using TemporalData. I am simulating a two state system, and every time the system goes into a new state (which happens randomly), then I put ...
0answers
57 views

### Arrays with two different types of indices

Is there a way of having arrays which have, so to speak, two different depths $m,n$? From the point of view of memory usage, it would be the same as an array of depth $m+n$, but I would like to ...
1answer
120 views

### Turning table into association for Classify

I have the following sample data for 20 users. I know their sex, and the response for three yes/no questions. I am trying to building a classifier to guess their response to the third question, based ...
2answers
139 views

### Short way to query Dataset by the value of several columns

I learned how to query Dataset for rows that contain a certain value, but now I need to query for a long series of And in chain ...
4answers
594 views

### How to get complete Documentation Center graph of guide pages?

On the very last image below you can see a typical path of walking through Documentation Center guide pages. What is the best way to get the graph data and visualize the whole structure of these ...
3answers
353 views

### Selecting numbers from a list

If I wish to select numbers which are greater than 2 or less than 1, I use the following codes respectively: ...
1answer
5k views

### File-backed lists/variables for handling large data

Background Currently I am working with some large data (most of it generated by Mathematica itself). I usually find it a hassle to do this. For example, I just exported a large amount of data to ...
3answers
1k views

### Error changing Dataset using Part

Update It was a bug in the documentation of V10.0, this functionality was not implemented yet, and V10.1 changed the documentation, removing it. It's a pity, because it's a very useful operations, ...
2answers
799 views

### Dataset vs an association of associations

Associations with a record structure (e.g., a flat table) can be organised in one of two main ways. First as a list of associations, which is also used in the case of Mathematica's data set ...
3answers
926 views

### Converting hierarchies of rules to associations

The impossibility of MatchQ-ing inside and Association MatchQ-ing Associations (MMA 10) explains a problem I have. I would like ...
0answers
112 views

### Custom Head for Encapsulation

Often when I'm writing a project in Mathematica, the number of arguments I must provide to functions spins out of control. I need a sort of object-oriented encapsulation approach. I've already had a ...
0answers
244 views

### Integration of graphs with datasets

Mathematica has a rich family of graph algorithms. I would like to leverage some of these for a very large tree structure. Because of the size of the structure, I would like to store it in a Dataset ...
0answers
110 views

### AVL binary search tree implementation

Is there any text-book implementation of self-balancing binary search trees such as AVL or red-black in Mathematica?
1answer
280 views

### Why do lookup times in Dataset and Association differ by orders of magnitude?

Consider the following three data structures: a list of rules, an association, and a dataset: ...
1answer
140 views

### Import and export without changing number format

I have a complex file that is the output of a program. The file contains multiple columns with data in different number formats. For example: ...
0answers
121 views

### Does Mathematica support an unordered set (e.g. hashset) data structure?

Does Mathematica support any data structure representing an unordered set (without multiplicity) of Mathematica expressions? I would like this data structure to support $O(1)$ insertion, deletion, and ...
0answers
59 views

### Does Mathematica support out-of-core Associations?

I often find myself collecting data in an Association[] which outgrows my computer's main memory. Does Mathematica support any out-of-core equivalent? Ideally, I ...
2answers
199 views

### Entropy of the elements of a general data set

I have the following data set, and wish to track the evolution of the entropy of each element within the set. I have evaluated the entropy for some elements, but how does one evaluate the entropy of ...
1answer
280 views

### Why won't SparseArray let me store values with the head List?

When you attempt to define a SparseArray with elements that have the head List it complains: ...
5answers
722 views

### How can a big table be treated as a database?

I often work with big tables that I want to treat kind of like a database. Here's an example table. ...
4answers
119 views

### Deleting or replacing inner elements depending on higher level elements

Consider a data structure like: ...
7answers
10k views

### Struct equivalent in Mathematica?

I really miss having something like a struct in Mathematica. I know of (and regularly use) a couple of programming techniques which feel like a ...
1answer
153 views

### ordered tree data structure

I have a map $f:X\to \mathbb{N}$ and I wish to find $x,x'\in X$ such that $f(x)=f(x')$. Since such elements are rare, I will have to check very many elements and perform many comparisons, so I suspect ...
1answer
114 views

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1answer
146 views

### Parsing string with nested information

I am trying to parse a string, but I have no idea how to solve the following problem ...
2answers
488 views

### How would I programmatically add a row to a Dataset?

I would like to use a Dataset to track the process of a lengthy calculation over a large volume of material. Dataset appeals to me because of the power of the queries and it also looks like it may ...
1answer
169 views

### Filtering Query Nested Data (Dataset and Association)

I am trying to filter a nested Dataset. I have some data that looks like this (curated for this example): ...
2answers
1k views

### Can a Trie be implemented efficiently?

What is the most space and time efficient way to implement a Trie in Mathematica? Will it be practically faster than what is natively available in appropriate cases?