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
78 views

Double arguments and place of the underscore

Could someone explain me of this bit of code below is correct: Is it possible to define a function with a second bracket, see below, i.e. f[x_][y_]? And what does ...
0
votes
1answer
65 views

what do those signs #1, #1^2, #1^3, & mean here? [duplicate]

I have read common pitfalls page and the documentation page but I still don't understand what do those signs mean here? ...
11
votes
2answers
7k views

How do I identify the source of a “Tag times protected” error?

I have some code that looks like Table[ a = 1; b = {2, 3} c = i;, {i, 2} ] which gives an error: Set::write: Tag Times in c {2,3} is ...
4
votes
3answers
1k views

Orthonormalization of non-hermitian matrix eigenvectors

When using Orthogonalize[] one can specify which definition of "inner product" is to be used. For example, ...
2
votes
1answer
45 views

Why do Wolfram Alpha and Mathematica give different answers? [closed]

I've just got my hands on Wolfram Mathematica and tried to see if I can figure out how to use it by myself. I've plugged in an integral $\int \frac{dx}{(1-x^2)^{2/3}}$, knowing that the result is ...
7
votes
3answers
124 views

Morse Code Spacing

Trying to make a function to convert text into morse code and play the sound. Have it pretty much completed, but I cannot get mathematica to emit no sound so I can have a pause between the dots and ...
0
votes
2answers
76 views

Referencing elements of ArrayRules

How do I call elements of ArrayRules by their indices rather than by Part[ArrayRules[list],i]? I'd like to call the element that ...
3
votes
1answer
40 views

Aliases for keys?

The syntactic sugar for alternatives in replacement rules is clean: {a|b|c-> 1, d->2} Are there any analogous shorthands for keys in associations. I want ...
4
votes
1answer
101 views

Products of Differential Operators

I have a differential equation defined as the product of operators which I want to expand out into a polynomial in powers of $z\frac{d}{dz}$ $\qquad \prod_{n=1}^p(z\frac{d}{dz}+a_n)$ However when I ...
54
votes
1answer
1k views

Incompatible Changes since Mathematica Version 7?

There is documentation of the incompatible changes made to Mathematica with each major release: Incompatible Changes since Mathematica Version 1 Unfortunately that documentation simply stopped ...
0
votes
1answer
63 views

Fastest way to make division between a number and elements in a list [duplicate]

I have a list y={{a,b},{c,d},...} of dimension {10^5, 2}, and number x. I want to divide only the second part of each element of the list by x, and have as result a new list {{a,b/x},{c,d/x},...}. ...
0
votes
1answer
55 views

What does the syntax <<X>> mean? [duplicate]

What does the syntax; << X >> mean? Where X is a number? Cheers
56
votes
6answers
2k views

V10's Operator Forms - what are they good for?

V10 introduces an operator form for several functions perhaps primarily due to their role in queries as part of introducing data science functionality. At first pass it seems a lot of effort to add ...
2
votes
4answers
117 views
0
votes
1answer
50 views

Compile decreases the number of returned list elements

I have: LogisticMap = Compile[{μ}, ({μ, #} &) /@ Union[Drop[NestList[μ # (1 - #) &, .2, 300], 100]]]; Then: ...
0
votes
0answers
25 views

I would like know why “&” came after “FrontEndToken[”New"] here [duplicate]

I am a newbie to this Mathematica world who lives in South Korea, which is not a desirable place to have people to discuss Mathematica. So I came here, even though this question may look very simple ...
0
votes
0answers
52 views

What makes items with head `Function` different?

I apologize beforehand for the muddleheadedness of this question. It reflects the fact that I'm trying to interpret outward "behaviors" of Mathematica expressions without having any understanding of ...
3
votes
1answer
100 views

Binary decision diagrams (BDD) syntax error

I am new here (and to Mathematica) and would like to rebuild a simple binary decision diagram that I found here https://en.wikipedia.org/wiki/Binary_decision_diagram A code has been provided as part ...
5
votes
5answers
204 views

Nested function with an increasing argument

If, for example, I have a nesting function like Nest[1 + x^n (#) &, 1, 3] it gives the result ...
3
votes
0answers
36 views

Java anonymous functions from JLink?

JLink is really great to act on Java objects and access Java static methods. I'm asking myself if there would be a way to have access to a more recent Java syntax that allows anonymous functions, ...
3
votes
0answers
109 views

Assign variables from list inside With or Module

I have found that it is possible to assign variables from lists, as follows. r = {1, 2, 3}; {a, b, c} = r; b 2 However, ...
21
votes
0answers
401 views

A documented syntax of FileNames doesn't work?

Documentation discrepancy present through 10.3 According to the documentation for FileNames under Details: However when I attempt to use this syntax I get an ...
2
votes
0answers
51 views

Import names into notebook namespace [duplicate]

I have function that at some point has list of strings (e.g. {"apple","pear"}) and I want to declare (initialize) those variables in notebook namespace to default ...
7
votes
3answers
77 views

TagSetDelayed on a function with a delayed value

I'm trying to automatically optimize cases when the user evaluates Length[returnsList[x_]] to instead use returnsLength: ...
4
votes
1answer
166 views

Why assign variables to empty curly brackets?

I am trying to read code and I see empty curly brackets. For example: abc = {} or ...
6
votes
2answers
135 views

Ignore some values at return

Is there Mathematica analogue of Python _ (underscore) or Matlab ~, a special variable, that can be used when a function returns ...
6
votes
3answers
301 views

How can I create currying functions using pure function syntax?

For example how can I write In: pureFunctionSyntax[myF] /@ {7, 3} Out: {myF[7, Log[7]], myF[3, Log[3]]}
5
votes
3answers
601 views

Can symbols like + or * be used to denote the Plus and Times functions?

Can one do something similar to +[1, 2]? The point is that with one symbol you would be able to write expressions like ...
6
votes
2answers
464 views

What does (0 &) mean in an evaluation? [closed]

My Mathematica code is this: Simplify[D[Sqrt[1 + (u')^2 + (-60 x - 20 u u')^2], u]] It returns this: ...
48
votes
2answers
1k views

Head and everything except Head?

I have been working on picking expressions apart using Head and Part and encountered a little mystery. Consider the canonical ...
11
votes
1answer
144 views

The equivalent of dplyr mutate with Dataset

In R, there is a package "dplyr" that works on data.frame objects, which is one of the origins of the Mathematica Dataset construct. One of the things dplyr can do is "mutate" the columns of a ...
1
vote
0answers
57 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 ...
8
votes
0answers
84 views

Syntax error in debug mode

Bug introduced in 8.0 and persisting through 10.3.0 It appears that in debug mode, the \[Piecewise] symbol and its associated grid give a syntax error. For a ...
4
votes
2answers
95 views

How to define UpValues of NBSpline when the length of argument is unknown?

I mimic the built-in BSplineBasis[] to build a user-defined function NBSpline[], Namely, ...
37
votes
4answers
20k views

Is there a syntax for single-line comments for notebooks?

I'm aware that I can use (* ... *) to comment out stuff in a notebook. Many languages have a syntax for single-line comments, such as ...
20
votes
1answer
254 views

New AssociationThread forms in 10.2?

Bug introduced in 10.2.0 and fixed in 10.3.0 (The extension of AssociationThread is not (yet) implemented and the corresponding documentation has been removed) ...
1
vote
1answer
32 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
2answers
66 views

Intersection of all sublists of a list [duplicate]

I want to get the intersection of all sublists of list in an easy way. ...
1
vote
1answer
78 views

Can I map a function over a sequence of arguments without making the arguments into a list first?

I would like to set evenFunction[f_][a_, b_, c_, ...] = f[Abs[a], Abs[b], Abs[c], ...] I have come up with two ways to do this so far. Use pure functions ...
5
votes
2answers
280 views

f /@ # & /@ # & /@ # & /@ # & /@ # & /@ # & /@ # & /@ matrix

How can one write f /@ # & /@ # & /@ # & /@ # & /@ # & /@ # & /@ # & /@ matrix in one line with arbitrary level and without using ...
0
votes
0answers
40 views

Solving Integral -syntax or interpretation problems

WA interpreter achievement not well this entry from Mathematica, steps need to see the full resolution input WA ...
0
votes
1answer
111 views

Convert code from C++ to Mathematica [closed]

I need to know how to convert the following code in C++ to Mathematica. ...
1
vote
4answers
102 views

Build a truncated tower with numbers from 1 to 9 without repeating

consider the image subject to the following conditions appearing in my code, I find not the appropriate numbers ...
4
votes
2answers
111 views

Sorting and keeping the main format of list numbers [duplicate]

I have a list with these elements: list={1/2 (1 + Sqrt[5]), 1, 1, 1/2 (1 - Sqrt[5]), 0}; I want to sort them with ...
4
votes
0answers
79 views

Why does FromDigits transpose its argument (sometimes)?

FromDigits /@ Transpose@{{1, 2}, {3, 4}, {5, 6}} == FromDigits @ {{1, 2}, {3, 4}, {5, 6}} (* True *) The only "strange" syntax I've found in the docs is ...
0
votes
1answer
35 views

Possibly syntax errors? [duplicate]

trying to graph, however graph is blank when i enter it. Please help! ...
0
votes
1answer
157 views

Syntax::sntxf: “…” cannot be followed by “…\MatrixForm” [closed]

I'm trying to create a $3\times 1$ matrix named Pauli but I really don't understand what's the problem of the following code? ...
0
votes
1answer
52 views

How to store value of result in an array for a calculation inside the loop [closed]

Note: In my code I used j (ranging from 3 to 7) but I want j to be general I tried this ...