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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10
votes
2answers
500 views

How to create custom Graphics primitive?

How to create custom Graphics primitive? It should have the following properties, resembling properties of built-in geometric figures, like ...
0
votes
1answer
111 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 .. ...
1
vote
1answer
86 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
49 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
94 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
55 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
472 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
83 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
312 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? ...
1
vote
1answer
94 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 ...
0
votes
1answer
170 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 ...
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
168 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
76 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; ...
1
vote
0answers
118 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 ...
3
votes
1answer
116 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
124 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
103 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
117 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' ...
1
vote
1answer
213 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 ...
2
votes
2answers
106 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 ...
6
votes
2answers
2k 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. ...
4
votes
1answer
74 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. ...
0
votes
0answers
21 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 ...
1
vote
2answers
252 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 ...
6
votes
1answer
165 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 ...
3
votes
1answer
63 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
188 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
109 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
2answers
114 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
1answer
229 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 ...
1
vote
2answers
222 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, ...
6
votes
5answers
324 views

Is it possible to insert arguments into functions when they're used like Function@ or //Function?

Is it possible to insert arguments into functions when they're used like Function@ or //Function? Sometimes I need to do this, but then I have to return to the standard function usage: Function[] ...
4
votes
2answers
109 views
17
votes
3answers
646 views

How is + as an infix operator associated with Plus?

How is + associated with Plus? Suppose I want to define a head FooBar and have it ...
2
votes
2answers
229 views

Manipulate, Import external table, save as CDF, mail presentation

For my work I do data analysis. Most of these analysis are done on big databases with milions of records. I would like to make a manipulate (or animate) using a external dataset and create a CDF ...
24
votes
5answers
3k views
6
votes
3answers
278 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] ...
6
votes
1answer
201 views

Treat all variables as local in a module [duplicate]

In most languages, any variable defined inside a function is considered local. ...
2
votes
2answers
240 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
74 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 ...
9
votes
3answers
676 views

Difference between @ and @@

I am confused by the commands @ and @@. From the documentation, I learnt that @@ is the ...
4
votes
0answers
144 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 ...
3
votes
1answer
109 views
1
vote
0answers
37 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
122 views

Defining an operator

Let s be a positive integer and let DifferenceDelta be this function with step = 1. Define ...
0
votes
1answer
88 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
194 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
3answers
276 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 ...
30
votes
4answers
698 views

Usage of \[InvisibleApplication] and other related invisible characters

From the front end, \[InvisibleApplication] can be entered as Esc @ Esc, and is an invisible operator for @!. By an unfortunate ...