Questions on correct (or improved) formulation of Mathematica code to achieve particular results. Use this tag (not "symbol") for questions about all those odd @@ /@ # & and ~ characters.

learn more… | top users | synonyms

1
vote
1answer
80 views

integrating with multiple indicator functions depending on each other

I need to compute the following integral with three indicator functions, $I(x)$, $I_1(x_1)$ and $I_2(x_2)$, $$ \int_0^1\int_0^1I(x)\left( \ I_1(x_1)\,x_{1} + I_2(x_2)\,x_{2}-1 \right) dx_1 dx_2 $$ ...
1
vote
1answer
62 views

How to assign options to a variable?

I want to redefine a function similar to Plot like this: ...
1
vote
1answer
39 views

How to use Composition when the functions have two parameter

There are some basic instructions about Composition on this site, but I'm still confused on how to use it when the functions I am composing have two parameter, such ...
1
vote
2answers
103 views

Matrix with infinity on main diagonal

The question is trivial, however, there might be unexpected solutions. What would be nice way to create a square matrix with $\infty$ on main diagonal, and some arbitrary constant everywhere else? My ...
1
vote
1answer
68 views

NestList and RandomChoice from a list of functions

I am tryingg to modify Chaos Game Fractals from Wolfram Demonstrations. The part I am having problem with is this. Original code: ...
1
vote
1answer
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 <...
1
vote
2answers
161 views

MapThread with List Manupulation

I have the following three lists: ...
1
vote
1answer
252 views

Bincounting a list

I'm a Mathematica novice here. I'm trying to execute the following code to add random 1's into a zero matrix, repeat this many times, and then bin/histogram the number of nearest neighbor 1s. Can ...
1
vote
1answer
271 views

Syntax error: newline character interpreted as multiplication

I'm getting this error in Wolfram Workbench, and I don't know where it comes from: "Syntax error: newline character interpreted as multiplication" This error happens around an If[] function, in a ...
1
vote
1answer
215 views

Can I use Table without the appropriate bounds?

I´d like to use the Table command without defining n, so that I can have a list of n ...
1
vote
1answer
56 views

List of Inequalities in RegionPlot with different colors [duplicate]

Starting from the example of the Documentation: RegionPlot[{x^2 < y^3 + 1, y^2 < x^3 + 1}, {x, -2, 5}, {y, -2, 5}] Which gives a nice plot with two ...
1
vote
1answer
49 views

Basic Syntax Question — Variables for a function

I am looking at the following mathematica code Subscript[ff, r1_, r2_, CC_][x_, y_] := (r1 x + r2 y) (1 - (x + y)/CC) Subscript[gg, r1_, r2_, CC_][x_, y_] := x ...
1
vote
1answer
52 views

Using the Nest function — Confusion on my output

I have the following code and output where the original function is $f(x,a) = a^2 - x^2$. ...
1
vote
1answer
34 views

Scan appears to work setting graph properties, but get error on property-read

This is a self-contained version of something a bit bigger - going for brevity. It is a bit synthetic, but there are applications I have in mind where the {{1,2}} will be replaced with real data, more ...
1
vote
1answer
138 views

How to evaluate sum with different coefficient in each term?

I would like to know if there is a syntax that allows me to enter a sum that has coefficients that vary for every term? I have no interest in evaluating them numerically, but rather to keep them as ...
1
vote
1answer
152 views

GCD of Table entries

This question is from a newbie, so please be gentle in thrashing if I'm missing something very basic. How can I use GCD on a matrix/vector entries stored as Table. For example, if ...
1
vote
1answer
134 views

Partial derivative of defined function with vector input

Background: Have written a formula for the refractive index for a glass slab (n) that depends on the variables t,a and d. Now I want to calculate for example some sort of error and I'll be needing to ...
1
vote
1answer
59 views

What is the correct idiom for mapping a 0 value in a modulo n expression back to n?

What is the correct idiom for mapping the $0$ value in a modulo $n$ expression back to $n$. For example if I want to be sure that any integer value maps back to the index for a character in the ...
1
vote
1answer
27 views

SetterBar Display using MatrixForm

I have vAwGOptns = { {{0}, {0}}, {{1}, {0}}, {{0}, {1}}, {{1}, {1}} }; and would like to select ...
1
vote
2answers
65 views

How to get the outermost command evaluated first?

I have an expression like ToString[Stuff[...]]. I plan on having the Stuff[...] be manipulated as a string according to the output of other parts of the program. The problem is that Mathematica tries ...
1
vote
1answer
55 views

Correctly substituting a matrix into a scalar equation [duplicate]

I am having trouble correctly substituting a matrix into an (originally) scalar equation. For example: A = {{3, 1}, {1, 2}} cp = CharacteristicPolynomial[A, x] ...
1
vote
1answer
234 views

Correct usage of GeoPosition

My goal is to trace a ray down to the ground. I have done: ...
1
vote
1answer
74 views

Generating sequence of averages of averages of partial sums

I have been given the following code that generates the sequence of averages (of the partial sums) of Grandi's series: ...
1
vote
1answer
65 views

Display a triangle that rotates at certain rate when space bar is held down?

This question is a follow up on: Open a pop up window that runs a calculation in loop until it is closed? How can I open a pop up to show a picture of a triangle that rotates by ...
1
vote
1answer
56 views

RecurrenceTable [closed]

I got an error saying ...
1
vote
1answer
95 views

Cannot use Part in Pure Function [duplicate]

I need to select some lists in the nested list of form of {{1,2,3},{2,3,4}}. I have used Select to complete my work. But when I tried Position, it doesn't work. For example, ...
1
vote
1answer
419 views

Trying to calculate derivatives of spherical harmonics

I am trying to confirm what is shown on this website: http://functions.wolfram.com/Polynomials/SphericalHarmonicY/20/01/01/0001/ But when I type ...
1
vote
1answer
79 views

Appending functions to a list [duplicate]

Could someone please explain the difference between these methods, and possibly a nicer way to get the first result? (This is a toy example and in my real program I'd like to use ...
1
vote
1answer
105 views

Sort lists of vertices {indegrees, outdegrees} by indegree

in = VertexInDegree[F]; out = VertexOutDegree[F]; I want both in and out to be ordered by in. Example: graph has nodes a,b,c with indegrees 1,2,0 and outdegrees 0,...
1
vote
1answer
57 views

How to set the values into some variables from different lists [duplicate]

I have a list of Values and a list of variables. I want to set the Values into Variables. Assume the following code: ...
1
vote
1answer
447 views

Looping with NDSolve?

I have a series of PDE equations that are solved with NDSolve for certain variables $a$ and $b$ - Now, I want to see the output at a time $t$ as $a$ and $b$ change; so I was thinking of a loop ...
1
vote
1answer
349 views

Solve this equation symbolically

I am trying to solve the equation for the quantity r = y/x symbolically: 3/y^4 == 3/x^4 + a/(x + 2 y)^4 with the requirement that we need to perform the ...
1
vote
2answers
263 views

How to insert an expression in a Mathematica program?

I need to insert a very large expression in a Mathematica program. So I first Put[large expression,"file"] and then use Block[{}, Get["file"];...] to ...
1
vote
1answer
58 views

Mathematica Empty Plot FourierSinSeries function

I'm trying to get a plot of different order Fourier series of the function x-1, why does Mathematica give me an empty plot? ...
1
vote
0answers
47 views

Is it possible improve the code scanning beyond what SyntaxQ does? [closed]

Please, consider this package (* ::Package:: *) BeginPackage["HelloWorld`"]; a::usage="A"; b::usage="B"; Begin["`Private`"]; a=1; b= End[]; EndPackage[]; ...
1
vote
1answer
31 views

Iterating my function by $4$ using NestList — Syntax Confusion [duplicate]

I want to iterate my function $f(x) = 13xe^{-x}$ by $4$ multiple times. That is, $f, f^{4}, f^{8}, f^{12},\cdots$. Using Nestlist[f,x,4] I can get $f,f^{(2)}, f^{(3)...
1
vote
0answers
79 views

Meaning of Abs´? [closed]

A friend showed me the code below. r[i_] := {x[i, t], y[i, t], z[i, t]}; rji = r[i] - r[j]; solap = 2 a - Norm[rji]; FullSimplify[D[solap, t]] I'm unsure about ...
1
vote
0answers
397 views

How can I solve the 2D Laplace equation with Neumann boundary conditions? [closed]

I would like to solve the following boundary value problem for $u(x,y)$: PDE $\quad \quad \frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} = 0$ Domain $\quad \quad 0 \le x \le ...
1
vote
0answers
41 views

Mathematica Workflow [duplicate]

What methods/tools/tips have you found that dramatically improved your Mathematica workflow? I have a love/hate relationship with Mathematica. It is useful no doubt, but defies my intuition at every ...
1
vote
0answers
53 views

Using Nearest on a 2D List (seeing extra parentheses)

I am working a problem involving colliding particles. I define a list of particle diameters (effectively a bin distribution). I need to know if two particles collide, in what bin diameter should I ...
1
vote
0answers
93 views

SyntaxForm not correctly parsed by FrontEnd

When using TagBox with SyntaxForm, I noticed sometimes it is not well parsed by the FrontEnd....
1
vote
1answer
154 views

How would one minimize with respect to an unknown number of variables?

Say I had a function like the following: f[n_] := Sum[a + Subscript[b, k], {k, 0, n}] Such that ...
1
vote
0answers
194 views

Why is my answer being displayed with “Subscript^(0,1)[a,b]”? [duplicate]

I type in my equations using ctrl+- to make it look nice and my answer outputs in "Subscript^(0,1)[a,b]" form? What is going on? In the answer some bits are displayed with the actual subscripts and ...
1
vote
2answers
368 views

Changing Default Color for Titles, Sections, Subsections, etc., and Items (bullet color) [duplicate]

I'm new to Mathematica 9, and I assume there must be an easy fix for my problem, but I have not been able to find any yet. Essentially, I want the default color for the text of all of my titles, ...
1
vote
0answers
79 views

Decapitating “explicit” and “implicit” heads

This is a follow up to this question. So far, I named "explicit" heads to those that appear explicitly in the expression. For example, f[x] has an explicit head. I ...
1
vote
0answers
44 views

Matching Root[…] objects with patterns, unexpected hidden argument

I needed to write patterns that could distinguish between arbitrary-function and polynomial forms of Root objects, for example, ...
1
vote
0answers
147 views

Defining an operator

Let s be a positive integer and let DifferenceDelta be this function with step = 1. Define <...
1
vote
1answer
110 views

How to programmatically comment out multiple source files?

How to programmatically comment out the entire content of multiple .m source files assuming they start with correct Mathematica syntax? I need it to be robust so ...
1
vote
1answer
142 views

When is Evaluate needed within function arguments? [duplicate]

I'm trying to do a simple variable substitution within a ContourPlot, but it's not working. Here's an example: ...