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.

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0
votes
1answer
87 views

Populating an array with outputs of a function [closed]

I have searched, but didn't find much help on my issue. I have an optical physics problem that I'm working on .. ...
6
votes
4answers
169 views

How to select only NotebookObjects that are referring to ordinary notebooks? (not palettes etc.)

There is of course function Notebooks[] But, unfortunatelly it hasn't got useful options in this context. My question is how to pick ...
1
vote
1answer
80 views

Why there is no SlotSequence (##) form analogical to #[[ ;; n]]

I'm aware that this may be closed as offtopic but there are people around with "offtopic" knowledge :) So, in List context we can: ...
0
votes
1answer
137 views

Issue with Compile

The following code works fine with the the function f defined as a module, however, when I convert it to be a compiled function, it gives me errors. Can some one ...
8
votes
1answer
113 views

Head of a MatrixForm expression?

An example in http://www-zeuthen.desy.de/theory/capp2005/Course/hahn/mathematica.pdf amounts to the following ...
0
votes
1answer
40 views

Convert variable into function

Sorry if this is a duplicate, but I have a variable called H. H is some complicated function of ...
2
votes
1answer
83 views

MapThread over a nested list

This may be a simple question. Please close it if it is already answered. I have a nested list kr = {{35, 32, 27, 20}, {36, 33, 28, 21}, {37, 34, 29, 22}} I ...
0
votes
1answer
40 views

Square root of a value defined in a finite field?

I am trying to find the right way to compute the square root of a number defined in a finite field. For example, ...
5
votes
2answers
386 views

Multiply each element of an array by another array?

I would like to multiply an array by each element of another array, and am having a lot of trouble finding a built-in or automated method of doing. Here is an example of what I'd like to achieve: ...
0
votes
0answers
53 views

g00 (metric tensor) not explicitly evaluated in FeynCalc

I am learning Mathematica and FeynCalc by doing some basic cross section calculations. I have an issue with trace calculations: When I plug in for instance the ...
1
vote
4answers
202 views

Finding a number which has the same remainder when dividing certain other numbers

I am having some trouble with formulating my problem in Mathematica for this question: Is there a number greater than 1 which leaves the same remainder when it divides into 1716, 2154, and 4271? ...
0
votes
0answers
37 views

Using derivative d in Mathematica [duplicate]

In mathematics derivates are often written like $$d^2y \over dx^2$$ or $$dy \over dx$$ In Mathematica we have the function D, but is it possible to use a similar approach?
0
votes
0answers
41 views

Using Table[ ] vs using Do[Append [ ] ] [duplicate]

Is it generally better/faster to use the Table function over using Do[Append []]? For example, I have this piece of code: ...
3
votes
2answers
133 views

How to define the irrational domain or any other arbitrary domain?

I have found no way to define the domain of Irrational numbers. I can easily define a test to see if a number is irrational by defining: ...
0
votes
1answer
74 views

How to write series of Do[ ]'s with a single Table[ ]?

Edited to provide more information (sorry I don't know how to format matrices here) I would like to replace: m = 4; ...
0
votes
0answers
84 views

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

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
1answer
126 views

KroneckerProduct and Transpose [closed]

I need to take the KroneckerProduct of the an $n \times n$ identity matrix and a $1 \times n$ row vector (let's call it $T$), both of which are numerical. As in: ...
3
votes
1answer
100 views

Differentiating a Dot Product

I apologize if this type of question has been asked before, but a preliminary search turned up nothing. I would like to differentiate dot products. For example, consider taking a derivative with ...
0
votes
2answers
120 views

How to display output as symbols?

I have this piece of code which populates a matrix following different rules depending on row and column number: ...
3
votes
1answer
98 views

Why is ^^ff not the same as ^^ToExpression[“ff”]?

I want to convert a hexadecimal string to a decimal (base 10) number: 16^^ff 16^^ToExpression["ff"] The 1st line returns the correct answer of 255, while the 2nd ...
0
votes
1answer
101 views

Holding Input Windows

I am creating a Mathematica document which contains a list of proofs in various fields of Mathematics so that I can easily review whenever I would like. First, I create a large set I call 'proofs' ...
2
votes
2answers
101 views

Return only one numeric solution to equation [duplicate]

Consider a simple plane equation 2x-3y+4z==7 I just want some position vector on that plane. For example, {7/2,0,0} would be ...
1
vote
1answer
154 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 ...
6
votes
2answers
951 views

How to reverse the direction of the y axes

I have a similar question to this one. Unfortunately, the answers there didn't help me. I would like to plot a simple function with the normal Plot function. ...
0
votes
1answer
165 views

Please explain this code (contains Append, Do, Coefficient)

I am a graduate student using a past student's Mathematica program. Will someone please explain to me exactly what this piece of code is doing? Specifically the ...
4
votes
1answer
69 views

Dot when used in a pattern becomes Times… Why?

In[1] := Hold[a.b] // FullForm Out[1] := Hold[Dot[a,b]] So far so good. ...
5
votes
3answers
967 views

Matrix Multiplication in context of row and column vectors

I've been looking at some matrices in Mathematica and I've noticed something very weird: They're extremely temperamental when it comes to dot products! For example, if I have the following, ...
0
votes
0answers
20 views

Incorporating Built-In Function Options/Parameters into Shorthand [duplicate]

Shorthand syntax provides an alternate way to apply functions and, in many cases, improves readability. A simple example would be ...
6
votes
1answer
150 views

How can I define a ⊕ operator?

What is wrong with the following code? CirclePlus := SparseArray[Band[{1, 1}] -> {##}] & a_ ⊕ b_ := CirclePlus[a, b] SetDelayed::write: Tag Function in ...
1
vote
2answers
199 views

Conditional range in a parametric plot

I have a program that needs to be done like this: ParametricPlot[ equation, If[x < 1, {x, 0, t}, {x, t, 2}]] But Mathematica didn't seem to recognize the ...
3
votes
1answer
61 views

Pathological behaviour when evaluating a sum

When I declare the function $f$ as follows: f[n_] := Sum[x/Sum[Sqrt[y], {y, 1, x}], {x, 1, n}]/n the input ...
1
vote
2answers
181 views

Making nice code: choosing one of several procedures

Happy new year mathematica gurus of stack exchange! As I see it one of the major obstacles in getting decent at programming mathematica is that, not only do you need to learn how certain commands ...
6
votes
1answer
106 views

Why can Format be used on the left side?

I am learning Mathematica in random order by reading its documentation. This approach is what I like most when learning new things. Consider the following 2 cases. Syntax A: ...
3
votes
3answers
137 views

Is it possible to use infix notation ~ for functions with one argument or more than 2 arguments?

According to a Mathematica textbook, we can write N[x,n] by using infix notation as x ~ N ~ n. How about other functions with ...
1
vote
2answers
173 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, ...
2
votes
1answer
225 views

What are the min and max arguments to EdgeDetect?

What are the min and max arguments to EdgeDetect, for all methods and specifically "Sobel"? How do I find the limits or ranges ...
4
votes
2answers
89 views

Limit won't compute

Does anyone know why the limit: ...
6
votes
3answers
254 views

Finding the square root of a squared number?

Taking the square root of the square of a number Variable set to a real value I'm wondering why these examples a = -4.3; Sqrt@a² Sqrt@(a^2) Sqrt[a^2] Sqrt[a²] ...
5
votes
1answer
151 views

Treat all variables as local in a module [duplicate]

In most languages, any variable defined inside a function is considered local. ...
3
votes
2answers
111 views

Why does the iterator index in Table not work here?

I type the following command line Table[D[#1,varx[[i]]] &,{i,3}] where varx is a vector of dummy variables ...
2
votes
2answers
193 views

import a list of replacement rules

I have a text file with a set of replacement rules, of the form x^3y^2 -> 4, xy^2 -> 2, ... for example. I'm having some issues trying to figure out ...
1
vote
0answers
71 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 ...
7
votes
3answers
464 views

Difference between @ and @@

I am confused by the commands @ and @@. From the documentation, I learnt that @@ is the ...
4
votes
0answers
120 views

Syntax error for optional pattern, but only in debugger

This expression (explained here by Leonid) evaluates fine unless Evaluation->Debugger is enabled: h[x : (_Integer) : 1] := x Syntax::sntxf: "x:" cannot be ...
1
vote
0answers
36 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
107 views

Defining an operator

Let s be a positive integer and let DifferenceDelta be this function with step = 1. Define ...
0
votes
1answer
86 views

Plot producing many error messages when given complicated function

I'm new to Mathematica and am running in to all sorts of silly difficulties with coding in it. I'm trying to calculate a function f[x, k], normalise it with another ...
2
votes
4answers
172 views

Where did I go wrong with my implementation of finding a plane tangent to a surface?

I am working on finding the plane tangent to a paraboloid at a given point. My code: ...
6
votes
1answer
77 views

Why only up to two \[Prime] superscripts are interpreted as derivatives?

I noticed that only up to two \[Prime] superscripts are interpreted as derivatives. Is there a reason for this restriction? Is it documented? ...
6
votes
3answers
250 views

Where did I go wrong with my implementation of the trapezoidal rule?

One method for doing quadrature, called the trapezoidal rule, improves accuracy by connecting the points on the curve corresponding to the points of subdivision with line segments, forming trapezoidal ...