# Tagged Questions

Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.

432 views

### Learning Resources for Data Science in the Wolfram Language

I'm delivering an upcoming course on Data Science with the programming/analysis done predominantly in the Wolfram Language. I created the following table to leverage students' familiarity with Lists ...
232 views

### Strategies to find curves on messy data using FindCurvePath

I have a set of data points that correspond to roots of a transcendental equation with respect to a parameter (the abscissa) which, by the properties of the system, define continuous curves (might be ...
149 views

Executing: ...
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### Efficient way to flatten or transpose-arrayreshape tensors

I have a tensor of dimensions $(2, 100, 100, 2, 100, 100)$ and I want to reshape it to a form of $(2*100*100,2*100*100)$, e.g. Flatten[A,{{1,5,6},{4,2,3}}]. If I ...
121 views

### TimeConstrained[Delete[Range[1],1]] causes kernel crash

Run these two samples of code here (AFTER SAVING YOUR CURRENT WORK): Do[ TimeConstrained[ While[True, Delete[{1}, 1]; ];, 0.1];, {100}] ...
467 views

I want to download historical S&P 500 stock prices and combined them into one big file, having only one column of date referencing all stocks. Here is what I have do so far. ...
57 views

### SimilarityRules for SequenceAlignment of two lists

I am trying to use the SimilarityRules option of SequenceAlignment to customize its output. This works perfectly for strings, ...
64 views

### Create an adequate 'training set' to train a ClassifierFunction which performs the role of the built-in SubsetQ

I am trying to "grow" my own SubsetQ function using Machine Learning methods. My cSubsetQ when given two lists (listA and ...
101 views

### Bug in ListLinePlot[] when Filling up and down?

I'm trying to understand this apparently incorrect Filling behavior in ListLinePlot[]. Evaluating this ...
122 views

### Gather dependency on list order?

I get intrigued about Gather behavior on this post. I thought that Gather was invariant under list order? Here is the result I ...
264 views

### Strange behavior of undocumented RawArray and ArrayObject expressions

I discovered several strange results and inconsistencies while trying to understand what undocumented RawArray and ArrayObject ...
74 views

### Kernel crashes when computing finite difference mixed derivative with respect to y & z but works fine when computing with respect to x & y or x & z?

I am using Mathematica 10.4.0 on Ubuntu 16.04. I am trying to solve a set of differential equations using finite difference method on an NxNxN cubic grid (x, y, z directions). I am getting a weird ...
57 views

### Weird behaviour for a vector InterpolatingFunction inside an NDSolve

I have run into some weird behaviour on the part of NDSolve which I find pretty bizarre and which I would like to understand better. Suppose, for the sake of ...
450 views

### Taking real and imaginary parts of indexed functions and speeding up ComplexExpand

I am setting up a large system of ODEs and in order to use the IDA method (which is sig. faster for my system and thus attractive), I must split my equations into real and imaginary parts. I am ...
70 views

### Function output

I would like a function that computes Cartesian product of two sets z=(Tuples@{#1,#2}), and computes the number of elements in this set(list) ...
91 views

### Fast construction and reshaping of large tensors

I'm trying to construct a large matrix which is derived from some higher rank tensor (the rank of interest to me changes case by case, so it needs to be a general method). Currently, the process of ...
76 views

### Compilation of a function that needs to call Subsets

I'm working on a code that runs many (easy) operations on combinations (subsets) of different size (6, 7, 8, 9) taken from a big set of numbers (normally more that 40). So, this means the code has to ...
71 views

### Choosing a List as VertexWeight for a TreeGraph

I would like to map every vertex of my TreeGraph to an List. ...
114 views

### ParallelTable and expensive functions

I would like to build up a 2D-Table using ParallelTable as follows ...
268 views

### Faster Ways to compute recursive summation

It takes a long time to compute the summation below, and I'd like to know if there are some better ways to compute things faster. I have used $3$ ways to calculate, but they are very unsatisfactory. I ...
76 views

### The number of real values assumed by combinations of complex roots of a decic

Define complex conjugate as the pair of complex numbers $a+bi,a-bi$. Assume you have 5 such pairs and they are the 10 roots $x_i$ of a 10th-deg equation with integer coefficients. In general, how many ...
474 views

### Generating a function which outputs possible chemical reactions

I want to make a list of chemical reactions and I write them down in a $\require{mhchem}\LaTeX$ format. They are of the following form NA_n^i+MB_m^j \rightarrow \hat NA_{\hat n}^{\hat i}+\hat ...
62 views

### DeleteDuplicates

After having applied "DeleteDuplicates" to a list of data (15000 rows per 3 columns), when I try to interpolate that list of data it gives me back again: "There are duplicated abscissa points in.." ...
60 views

### Distinguish hashtag # operator when using multiple functions

I would like to do this list = Append[list[[#]],Map[list2[[1, #]] & , list[[#, 4]], {2}]] & /@ Range[Length[list]]; But I would like to substitute ...
43 views

### List manipulation, averaging over lists and fidelity

I want to create vectors from a function poly[α_, β_, δ_, ϕ1_] were several variables (α, β, δ) are randomly sampled from a unit sphere. Then I want to vary another ...
50 views

### Estimating processing time for commands

I am trying to evaluate some equations by using Taylor series of expansion (Series[], ExpandAll[], and Normal[] command), and using n equation and n unknown (Solve). Following is not full command (if ...
33 views

### Using Coefficient for Conjugate[variables] (Mathematica ignores my assumptions)

I have a sum and I use Coeffcient[] to extract certain terms. For example, I want all term in the following sum that contain ...
50 views

### Concise use of list addressing

I very often work with Lists of Lists (trend data exported from other programs). Sometimes the start times of the important data ...
61 views

### Finding correct combination of functions

I am trying to write code where I have an array $S$ or numbers in any order [5,4,2,1,....] Then I have a specific set of functions that I can write. ...
78 views

### Lower memory usage and speed nested loops

I'm trying to make some tracking with Mathematica. ...
50 views

### Generate a list of values of a function for each value of the parameters already found

The following question is an extension of this question Find all roots of a function with parabolic cylinder functions in a range of the variable. Now I want to use the roots found to calculate a ...
62 views

### Problems with indexes in a Do-cycle and CoefficientArrays

I have a system of linear equations with variables $A_n$ and need its coefficients in a matrix form (Transform linear system into a matrix form). I'm trying to do that through a ...
75 views

### Tracking solutions over a Brillouin zone

Thanks to @bbgodfrey I have a function that finds the two solutions to a set of equations bounded by a hexagonal region (corresponding to the Brillouin zone). It takes the angle ...
102 views

### Disease Network Model Using NDSolve

I have a basic disease model using NDSolve: ...
41 views

### FirstPosition returning an error message together with the correct answer

I have the following code: ...
99 views

### Find algorithm or generator formula with automated procedure and pattern recognition

I am trying to find a generator formula for the discriminant of a polynomial and believe it would be an interesting problem for the Mathematica community to know how to automate evaluation of certain ...
132 views

### Autocorrelation of 3D Points

I'm trying to compute the autocorrelation of a list of points $(x,y,z)$ in 3D. Can the CorrelationFunction or maybe ...
120 views

### How to create a complex variable from dated list values

Can anyone help me to construct a variable "PI" from values of variable x. Variable x represents a group of two time series rj and ri on equal dates(joined two dated lists with states).Variable x have ...
65 views

### A more efficient way of fitting a non-linear model that returns an entire list?

I have a function that takes two parameters, del and nu, and returns a list npoints long ...
453 views

### Convolve two sets of (x,y) data sets

I have two sets of data in the form a={{.1,2},{.2,3},{.3,4},{.5,6}} b={{0,8},{.1,4},{.2,7},{.3,1},{.5,10},{.6,3}} Both data sets have even spacing, although ...
121 views

### New list generated from the sum of elements taken from two lists

I have been using mathematica for a while, but I have problem wrapping my head around list manipulation functions. I would appreciate any suggestions. Here is what I want to do. ListV is a list of ...
104 views

### Optimized subset algorithm implementation

I was reading a paper from Mathematica Journal.It mentions a code for calculating subsets. ...
160 views

### Why doesn't ParallelMap improve the performance of FoldList?

This question arose during my analysis of the following problem: filling gaps. (The code used here is Simon Woods's work.) FoldList seems to not cooperate with ...
31 views

### Pass List / Vector argument through NDSolve to a function

I am trying to pass vector or list as argument to the function from NDsolve.And I am getting these error. Also I am pretty new to stack overflow. Apology if this a possible duplicate. Here is my code. ...
27 views

### factoring a phrase of matrix elements and calculating main eigenvalues

I have a question containg two parts: 1-If we have a matrix as ...
39 views

### Do[If[ *stuff* ]*arguments*]: Increasing range over which Do iterates changes results of If?

Summary: If I run the same Do[] expression but with the variable(s) over which I am iterating taking on more values (but same increment), an If statement inside the Do[] evaluates as false a few times ...
31 views

### Envelope of a given table (or plot)

Is there any way to construct an envelope of a given table (list) or plot? For example, I have plotted (used ListPlot of txt-file) And then I want to plot the envelope (upper or lower) of this plot ...
80 views

### How to Extract and Rearrange Elements in Doubly-Nested Lists

Hopefully any easy problem for you guys to help me with! I'm currently having an issue with writing some Mathematica code that will extract the each nth element in each array within a matrix, and then ...
I'm new to the Wolfram Mathematica language. I want to program a dynamic set of numbers in such as: $S={\frac{1+n}{a}=\frac{1}{a};\;\frac{2}{a};\;\frac{3}{a};\; \dots ;\;\frac{1+n_{max}}{a}}$, where ...