# Tagged Questions

Questions on writing non-trivial programs in Mathematica. Do not use this tag for questions on plotting/graphics or for questions on doing mathematics with Mathematica, where the focus is more on the math than the program.

70 views

### Implicit region is not “valid” in ParamatricNDSolveValue function?

I am trying to solve a geometric problem with relation to my Schrodinger equation and its boundaries. Here is my code: ...
216 views

### How can I create a 3D representation of an object with known coordinates and adjacency table in mathematica?

Basically I want to create an object with specified coordinates and adjacency table, like in page two of this article. I'm completely new to using Mathematica, any help would be great! EDIT: So I ...
344 views

Today, I read a good web page about love which owns many beautiful pictures. It is fussy for me to download every picture hand-by-hand, so I'd like to use Mathematica to do this case automatically. I ...
87 views

### Retrieve rendered graphics via WSTP

I am planning on using Mathematica as calculation and rendering backend for an application, i.e., call Mathematica via WSTP and use EvaluatePacket to have it ...
143 views

### How to extract both first and last rows of each group from unbalanced panel data

This is a follow up question form my last question click here. I have unbalanced panel data such as : ...
229 views

### How can I overload a function with multiple bracket-slots so f[a][b] and f[a] can coexist?

Maybe this is not even possible: I want to create a function f that can have two input brackets like: f[a_][b_:1]:= a*b and ...
217 views

### How can a function know in which function it was evaluated?

Hello my second question here might be very hard. I am asking for something "magical", if i define a function g and i call it inside a function f, how can g have information about the outer function ...
94 views

### Need help updating an old Mathematica worksheet

I found a notebook that symbolically applies the multiple time scales method to any differential equations. I don't like just using other people's code so I am going through the author's work line by ...
497 views

### Find permutations with constraints without using Permutations

EDIT: To clarify, the bottleneck right now is available RAM, so any answer should keep that in mind (I cannot store all T! lists of length ...
63 views

### Trying to write a program to find an approximate harmonic function on a given graph using relation method

So given an undirected graph with two vertices that have fixed values assigned to them, a harmonic function is a function that assigns values to all other vertices such that the value assigned to each ...
97 views

### How to improve this function that selects parameters from arbitrary distribution using Recursion?

Below, I have defined a function using Which to select model parameters based upon various conditions. My questions are: Is there any danger in writing this function using Recursion? Is there a more ...
139 views

### Perceptron: Do loop not returning a value

I am trying to write a function that finds a simple best fit line for some data (Perceptron algorithm). Sadly it returns no output at all. Here's the code below: ...
186 views

### How to plot points with error circles on map with latitude/longitude grid

I am currently working on a project to model the location of icebergs in the northwest atlantic. When an iceberg is sighted, an error circle is plotted around it (with a bivariate normal probability ...
145 views

I would like to access Mathematica functions from within a Fortran program. I am unsure how to start (which is probably related to my lack of up-to-date Fortran knowledge). Is it necessary to write a ...
94 views

### Hypothesis Testing and Formatting Output

I am trying to write a function that tests hypotheses and gives me a nice table but I can't. I need forum's help. For example, I have the following data ...
233 views

### How to construct custom operators with precedence?

I need to combine data structures in operations analogous to addition, subtraction, multiplication and division (and more). I need more than one operation of each type, i.e. more than one method of ...
541 views

### How can I invoke the solution of NDSolve to determine a parameter in my equation just inside NDSlove?

I am trying to solve a differential equation by NDSlove for $h(x,t)$. It reads $$h_t=h_{xx}-V_h-\lambda(t)$$ where $V_h$ is a given function of $h(x,t)$ denoted by <...
78 views

### Ways to protect certain parts of expressions

I am currently working on a quantum mechanics problem where I try to find equations that relate different states of a many-body system. The states are described by sets of pairs of integers, like <...
25 views

### Iterating a model with 2nd order difference equations using Manipulate [duplicate]

I have a model including first and second order difference equations. It works for the case of first difference equation, which is below: ...
169 views

### Nested mapping of a function

If I use the construct f[#] & /@ f[#] & /@ f[#] & /@ {a, b, c} my function works, but if I use ...
146 views

### Finding column-wise ranks of values in a multidimensional list

I often have to find ranks of values in a list. However, Mathematica does not have built-in functions for that, or may be I'm just not aware of them. I can easily find ranks of a row/column vector. ...
44 views

### Why does this cause an error? [closed]

In[73]:= f[x_] := Save["C:\\Users\\user\\Desktop\\file", x <> x] f["###"] During evaluation of In[73]:= Save::sym: Argument ###:f3b5.01<>.01:f3b5###:...
436 views

### Easiest way to create a binary variable

Binary variable is often used in applied statistics. However, I had a hard time to figure out how to create it. Somebody might have better idea how to do it. I have two variables say x and y as ...
128 views

### Simulations using alternative initial conditions

With help from some of you guys here in this forum, I have developed the following code, which works perfectly. My questions are: how to automate the simulations with varying initial conditions. In ...
144 views

### Using FindMinimum with matrix input

I define the following function which spits out a number S when I feed it a dxd square matrix: ...
103 views

### How to efficiently find parts of a string with beginning and ending specified?

I'm trying to find specific URL addresses from a html document. The addresses can be found between the strings "href=\"" and "\" class=\"listing". The problem is not including strings like this: "href=...
117 views

### converting DO loop into NestList form

I would like to rewrite this Do loop using NestList. Can you help me? ** DO loop ...
114 views

### Modifying Game of Life code so that the lattice can be seeded with life forms

I want to modify Game of Life code so that the lattice can be seeded with one or two new life forms like: ...
193 views

### Copy Built-in function to new name

It is know that some built-in functions are system function and changing their properties may cause trouble. Suppose for example I want to change features of Cases: ...
120 views

### How can I do multiple (double) integral with periodic boundary conditions?

I am trying to do a simple double integral $\int_0^l \left[\int_0^l h^3 h_{xxx}dx\right]dx$ with periodic boundary conditions $h[0,\tau]=h[l,\tau]$ $h_x[0,\tau]=h_x[l,\tau]$ \$h_{xx}[0,\tau]=h_{...
238 views

### NDSolve with initial condition: initial conditions did not evaluate to an array of numbers of depth 1(for 1D) or 2 (for 2D) on spatial grid

I have the following naive code to solve a PDE in two spatial dimensions (x,y) with periodic boundary conditions: ...
183 views

### ControlType -> None Vs. Module inside Manipulate (i.e. making everything local)

I'm building a program on another one made available in the Wolfram Demonstration Project. I've noticed that in the original code (working flawlessly) many variables were made local inside the ...
409 views

### For a given expression: if it appears, remove it, but if it is absent, add it

While reformatting Szabolcs's code from (42660) I noticed this interesting operation: ...
78 views

### Are there methods to serialize and deserialize large calculation runs? [closed]

I have a fairly large calculation to map an electric field over large areas (square kilometers). This runs for a fairly long time. Are there ways to serialize the current state of a running ...
38 views

### New output cell generated for each run of a GraphicsGrid - is there a way to simply update the same output cell each run?

I have a Code cell that generates a set of plots in a GraphicsGrid[]. Each time I execute the Code cell, a new Output cell is generated. Is there a way to simply update a single output cell instead ...
135 views

### Code turns dark blue after trying to run it [closed]

I have a large amount of data in my N-Body Code. I imagine Mathematica doesn't really like this, but is there any other reason for my code turning a navy blue colour after I try to run it?
80 views

### Define column types in a Dataset - Failure on append and Typesystem

I have a basic function that populates a Dataset according to user specified parameters. ...
271 views

### How would I obtain a list of column names in a Dataset?

I really love the addition of Dataset to Mathematica. I would like to write a basic utility function that exports a Dataset to Excel. Is there a way to get a list of column names from a Dataset?
491 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 ...
12 views

### all does not work [duplicate]

Thanks blochwave for giving me a detailed answer, but I have already used all these methods and none of them has worked well, it is clearly written in mathematica "get help" file that the Timing[] and ...
162 views

### How to speed up my code about Divisors?

This code is about PE496 In[21]:= ParallelSum[n*Count[Divisors[n^2], a_ /; n < a < 2 n], {n, 1, 10^5}] // AbsoluteTiming Out[21]= {5.987342,10724527832} I ...
193 views

### Finding CPU time of more than one expressions

I want to find the computational time (CPU time) of my code. When I use TimeUsed or Timing commands they give the CPU time of ...
101 views

### InterpolatingFunction used to work with mathematic 7 but not working with mathematica 10

This code is used to work perfectly with Mathematica 7 and now it is not working with Mathematica 10. Any help is appreciated. CL05 = InterpolatingFunction[{{0.5, 11.99999999999999}}, {1, ...
369 views

### Interactively inspecting parts of an object

There have been times when I want to find the structure of an object in order to extract some part of it. For example, extracting the x and y coordinates from a Graphics object generated by Plot. I ...
88 views

### How can I use manipulate on multiple lists within a function?

So I have my N-Body Problem set up like so, and I can plot it in ListPointPlot3D, but I cannot figure out how to stick this into a manipulate function. ...
468 views

### How to get short definition of all built in Mathematica Functions?

The first post in "Mathematica Weekly Newsletter - Tuesday, December 30, 2014" really attracted my attention as I was always looking for a complete list of built in Mathematica functions with short ...
510 views

### Collatz optimization

I'm VERY new to Mathematica programming (and by new I mean two days), and was solving Project Euler question 12, which states: Which starting number, under one million, produces the longest [...
289 views

### A problem about Steffensen method

Two days ago,I asked a question about bisection algorithm. Thanks for Michael E2 giving me a good solution My algorithm 1, I use the bisection algorithm to generate a initial value that contain a ...