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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2
votes
2answers
110 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
66 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 ...
6
votes
3answers
335 views

Difference between @ and @@

I am confused by the commands @ and @@. From the documentation, I learnt that @@ is the ...
4
votes
0answers
104 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
33 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
86 views

Defining an operator

Let s be a positive integer and let DifferenceDelta be this function with step = 1. Define ...
0
votes
1answer
82 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
152 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: ...
5
votes
1answer
69 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
232 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 ...
1
vote
2answers
111 views

Shortcut for Range[]?

I use Range a lot. Is there any syntactic shortcut for it, or do you always have to spell it out?
1
vote
1answer
90 views

Passing f[x][[1]] to FindRoot [duplicate]

FindRoot seems to fail for most examples of the form f[x_?NumericQ] := {x - 3 , x^3}; FindRoot[f[x][[1]], {x, 3}] ...
2
votes
0answers
36 views

Syntax for FrontEnd`SelectionSetStyle

I know FrontEnd`SelectionSetStyle is undocumented, but its name suggests it does what I need. What is its syntax? I have already tried several variations of the ...
2
votes
1answer
75 views

Is it possible to use a mathematical expression as function name?

This might seem as a silly question, but is it feasible to use a mathematical expression as the name of a function? For example, I'm studying the cross section of Compton scattering and there is a ...
1
vote
4answers
111 views

Help with writing a polynomial series [duplicate]

I want to write and evaluate an expression something like Sum[x[i] Product[y[j], {j(!=i), 1, n}], {i, 1, n}] but with correct syntax, where n is a any number ...
6
votes
1answer
85 views

Where does Documentation Center introduce the basics?

While helping a user who mistakenly thought that log rather than Log was the correct built-in function name, I included a ...
3
votes
1answer
151 views

Levels and slots

I am struggling with levels and #, if I understand this I think I will be able to grasp the entire concept. ...
2
votes
2answers
168 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 ...
2
votes
2answers
132 views

HoldForm[Operator ##] on some list

Recently in response to this question Mr.Wizard suggested an unusual way to summing numbers. This doesn't seem to be documented. ...
7
votes
3answers
557 views

Guidelines on giving readable names to variables [closed]

I know that one cannot use underscore to a variable name, like degree_of_The_First_Polynomial. But for a long variable name, it ...
0
votes
0answers
111 views

The /. syntax in numerical methods [duplicate]

I have an analytical approximation method for solving an ODE and want to compare this to an NDSolve solution, but the syntax is confusing me. To get the solution from NDSolve, I define the ODE as eqn ...
16
votes
3answers
446 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 ...
4
votes
2answers
156 views

Can someone explain this code for joining two lists by the first element of each sublist?

Background (which may be skipped, unless context is needed) I've recently begun learning Mathematica (and only up to chapter 3 of Wellin), but wanted to write some code to get a better feel for ...
11
votes
4answers
185 views

Constraint syntax compaction

Is there a more compact way to represent these constraints: NMaximize[{a+b+c,...
10
votes
1answer
167 views

Infix form of PutAppend ( >>> ) does not work with variable

I'm new to Mathematica, so I suspect this question involves either a misunderstanding involving variables or the usage of >>>. On a webMathematica page ...
2
votes
2answers
193 views

Writing a function that returns a (usable) function

I am trying to create a function that returns Arnold's Cat Map of size n iterated k times. I can get something out of the Function command, but I can't figure out ...
4
votes
3answers
358 views

What is the right way to construct DynamicModule

When I'm creating DynamicModules for CDF purposes I'm usualy basing on my experience with that, particular goal and content rather than on deep insight. I want to ...
1
vote
1answer
73 views

Why do two codes give different output?

I have tried the following to get the eigenvalues of several matrices of the type: ...
4
votes
1answer
67 views

Constructing an Array from typed expression

I want to produce an array from expressions given by test[one][1] = 3; . . test[one][5] = 7; etc. Normally would use ...
3
votes
1answer
101 views

How to make InverseFunction work on function defined with restriction on arguments

This example works to define InverseFunction on the first argument of a function ...
5
votes
2answers
209 views

Overlapping pure functions

Let say I need and option for Plot: RegionFunction -> (-6 < #2 < 6 &) But I also want those ...
-5
votes
1answer
148 views

Split dataset based on the first column [duplicate]

I have a dataset which I want to split based on the first column. The data looks like this ...
0
votes
0answers
141 views

Assigning numerical values to constants results in complex coefficients in Equations of Motion

I am using Mathematica to get the Equations of Motion (EOM) for a mechanical system (using Lagrangian Mechanics). While I get the EOM in symbolic form, on introducing the following code for assigning ...
1
vote
3answers
140 views

Equation values into list

Suppose I have a function say $f=x^2$. What I would like is a list (or even better, a list with a grid) which resembles {{1,1},{2,4},{3,9}, ...}. Ideally one should ...
20
votes
2answers
630 views

Why there is no name for #1@#2&?

Why does the pure function #1@#2& have no name? Is it due to the way Mathematica works, or is it "just because"? I'm asking because I find inelegant to write ...
4
votes
1answer
116 views

DeleteCases vs. DeleteDuplicates for removing points within a critical Euclidean distance

I'm attempting to remove all points in an array which are within a Euclidean distance "ThresDist" of one-another. Using the command: ...
22
votes
6answers
414 views

Constructing symbol definitions for With

I would like to be able to define two arrays, one containing symbol names and one containing the values of those symbols, for use in constructs such as With. For ...
2
votes
1answer
135 views

How to get 'exact' expression for result

I have a result from Mathematica for which want to have the exact expression, i.e. all of the arguments of type # replaced. It is given by: ...
1
vote
1answer
95 views

Correct usage of GeoPosition

My goal is to trace a ray down to the ground. I have done: ...
3
votes
1answer
141 views

Shortening the syntax {var1, var2} /. # & /@ list

I noticed that I often turn out to have a list of substitutions in the form ...
2
votes
2answers
127 views

Extracting counts of contiguous zeros and ones from a binary array

I'm a novice with Mathematica, but you guys have been very helpful to me in the past. I have a binary array [100, J repetitions] consisting of zeroes and ones. I'd like to extract a histogram of the ...
1
vote
1answer
153 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 ...
3
votes
1answer
90 views

Export file with semicolon at the end of line

Is there a rule that tells Mathematica to set a semicolon at the end of each line (except of the last one)? My MWE is: ...
3
votes
1answer
340 views

What do the hashtags represent in the result of Solve, and how should I use them? [duplicate]

There is a function that I'm trying to get the inverse of. My function is a simple polynomial: Tn[T_] := 4/9 T^3/Tc^2 + 5/9 T Now I tried to find ...
5
votes
1answer
160 views

How to convert an image to a compressed string representation equivalent to one copied to clipboard by `CopyToClipboard[image]`?

In my recent question I asked How to embed an image into a string? The suggested solution was ...
8
votes
2answers
320 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 ...
13
votes
2answers
346 views

How to embed an image into a string?

The documentation for String contains the following statements: Strings can contain any sequence of ordinary and special characters: … Strings preserve ...
5
votes
1answer
159 views

What does ` symbol in ClearAll[“Global`*”] mean?

I have found an example for clearing all symbol definition by: ClearAll["Global`*"] But what does the symbol ` mean? It isn't the apostrophe ', yet it is not ...
2
votes
0answers
159 views

NonLinearModelFit with Two Dimensional List of Weights

I'm currently trying to fit Planck's law (B[λ, T]) to measurements, thereby determining Planck's constant. I have a list of triplets containing wavelength, ...