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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6
votes
6answers
896 views

Can't comment strings with '*)' inside it

I believe it's a bug in notebook's comment parser. I can't comment strings with *) inside it. Something like: ...
6
votes
3answers
585 views

Syntax for prefix mode with multiple arguments using @ shorthand

Is it possible to use the @ symbol with multiple arguments? The Prefix command suggested not. If so, why?
6
votes
3answers
312 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]]}
6
votes
3answers
2k views

Keep function range as a variable

Plot[2*x^2 - x + 2, {x, -1, 1}] plots a function of x from -1 to 1. As far as I can see, I cannot "save" this range in a variable: ...
6
votes
2answers
173 views

How to Write Partition with Infix?

The documentation says that using Infix ~, the following input f[e1,e2,e3,...] can be rewritten as ...
6
votes
2answers
496 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: ...
6
votes
3answers
364 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
2answers
144 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
1answer
199 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 ...
6
votes
1answer
115 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: ...
6
votes
2answers
1k views

Constructing a Summation with a Variable Number of Inner Sums

I have a question regarding multiple sums. And my second index depends on the first index. Here it is: $$ \sum_{d=1}^{P}e^{-d}\sum_{\substack{1\leq k_{1}\leq Q \\ 1\leq k_{2}\leq Q \\... ...
6
votes
1answer
115 views

A question about two ways to use Default

Usually we define a function with default values by the syntax x_:default, but there is another technique to do this by registering a global default value with ...
6
votes
1answer
125 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
1answer
99 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 ...
6
votes
1answer
165 views

Problem overloading D[] using UpValues

First I define an entry of UpValues overloading D[] for expressions with head ftest: ...
6
votes
1answer
88 views

What is the role of _ in this expression?

I'm fairly familiar with basic Mathematica, but some of its more advanced syntax (especially certain special characters) eludes me. In the Scope section in the documentation of ...
6
votes
0answers
75 views

Negative accuracy numerics ( 0``-128 notation )

What does it mean to have a negative accuracy number? I understand 0``128 to mean "the number zero to 128 decimal points". Mathematica corroborates this: ...
6
votes
0answers
113 views

Design considerations behind `O` (a.k.a. BigOh, a.k.a. Landau Order)

This works without any warnings: O[Log[x]]. This raises a warning: O[x^2]. I have a few questions around this: Why is it a ...
5
votes
3answers
605 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 ...
5
votes
4answers
332 views

Multiple colors in Graphics[] environment

There are other questions on the site that are similar to this one, but the answers provided didn't help me. I want to draw disks of different radii. Each radius is the absolute value of a variable, ...
5
votes
5answers
214 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 ...
5
votes
3answers
249 views

How to imitate list comprehensions for constant arrays?

In Python, ['a'] * 10 generates ['a', 'a', 'a', 'a', 'a', 'a', 'a', 'a', 'a', 'a'] and ...
5
votes
3answers
262 views

Is it possible to make the Button execute two or more actions?

According to the help: Button[label,action] Is it possible to make the button execute two actions?
5
votes
4answers
328 views

Long list of similar rules

Given the following: ...
5
votes
2answers
270 views

Overlapping pure functions

Let say I need and option for Plot: RegionFunction -> (-6 < #2 < 6 &) But I also want those ...
5
votes
3answers
220 views

Relational operators on vectors

How do I use relational operators on vectors? {1, 2, 3} > {0, 1, 2} (*outputs {1, 2, 3} > {0, 1, 2}*) More generally, I want ...
5
votes
3answers
441 views

What is the right way to write a function that includes other functions?

I want to include multiple sub functions: $b(x) = 10x$ $w(x) = s + b(x)$ $c(x) = x^2$ into two main functions: $ua(x) = w(x)-c(x)$ $ub(x) = w(x)-c(x)^2$ As a reaction to this answer, I wrote ...
5
votes
2answers
212 views

Why SetDelayed won't work

I'm trying to do this: Riffle[list = {a, b, c, d, e, f}, tem = RandomInteger[1, Length@list-1]] {a, 0, b, 0, c, 1, d, 0, e, 0, f} But I think this method is ...
5
votes
2answers
219 views

Syntax highlighting conflict

I'm trying to syntax highlight this expression: x=$\sqrt{\pi }$//N and from various sources I've learned that x (the assigned symbol) belongs to context Global while the Pi and N belongs to System. So ...
5
votes
2answers
286 views

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

How can one write f /@ # & /@ # & /@ # & /@ # & /@ # & /@ # & /@ # & /@ matrix in one line with arbitrary level and without using ...
5
votes
2answers
243 views

Associativity of `/@` [duplicate]

Why are the following not equivalent: Map[Line, Map[(Print[#]; #) &, {{{2, 1}, {1, 1}}, {{-2, 1}, {3, 1}}}]] which produces ...
5
votes
2answers
411 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 ...
5
votes
2answers
633 views

Scalar product operator of complex vectors

What is the scalar product operator for complex vectors (or matrices) in Mathematica? The usual $Dot[]$ doesn't work. E.g. here is what the Mathematica gives $$\{1,0\}.\{I,0\}=I$$ but the answer ...
5
votes
1answer
245 views

Why does the Front End group backslashes into pairs?

What is \\ for? Help finds nothing on it. An odd number of backslashes greater than one are grouped by two and the last one is displayed with a different color. ...
5
votes
4answers
320 views

Defining a function with parameters as variables

I have an expression V = (a[1] + a[2])b[1]. How would I define a function of a[1], a[2] and ...
5
votes
1answer
99 views

Why are SetProperty and PropertyValue not working here?

I have a very simple graph, a loop: ...
5
votes
1answer
93 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 ...
5
votes
1answer
363 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 ...
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, ...
4
votes
2answers
887 views

Single dot textual form

How do I render a letter with a single dot above it? I see \[DoubleDot] and \[TripleDot] are readily available, but what about ...
4
votes
2answers
644 views

Write a function that returns the logarithmic derivative

How can we write a function that if we input an expression f, it returns the log derivative $\frac{1}{f} \frac{df}{dx}$. We have to use a conditional or pattern test so that the function accepts any ...
4
votes
2answers
421 views

List reversion inspired by Python

In python, if you wish to reverse a list, here is the trick: range(10)[::-1] => [9, 8, 7, 6, 5, 4, 3, 2, 1, 0] Note: ...
4
votes
4answers
273 views

Get Axes Range of Plot?

Say I have some plot plot = Plot[Sin[x], {x,0,10}] (*as an example*) Is there a way I can get the x and y axes min/max values from the "plot" variable? If I ...
4
votes
2answers
115 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
2answers
363 views

How can I avoid getting the error message Goto::nolabel in my code?

If anyone could suggest a reason why Label[begin] ... Goto[begin] would return Hold[Goto[Begin]], and (better) how can I avoid ...
4
votes
3answers
393 views

Brackets in output make unable to use output to identify matrix element

I'm trying to write a code where each matrix element swaps with a randomly selected neighbor (cardinal directions only) to redistribute the matrix. So far I've been able to replace an element with its ...
4
votes
2answers
296 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: ...
4
votes
1answer
180 views

Why assign variables to empty curly brackets?

I am trying to read code and I see empty curly brackets. For example: abc = {} or ...
4
votes
3answers
970 views

Integrating with multiple indicator functions

I am trying to calculate an integral involving multiple indicator functions, such as: $$ h(u,v,w) = -\int_0^1 J^{\prime\prime}(s) (I_{(0,s]}(u) - s)(I_{(0,s]}(v) - s)(I_{(0,s]}(w) - s)\, ...
4
votes
1answer
248 views

How to see abstract syntax tree of Wolfram Language expression

I mean, suppose I have this expression: 2 + 2 I want to get something like this: Plus[2, 2] as an output. I've tried FullForm, but this just evaluates 2+2 and returns 4. Is this even possible?