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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7
votes
2answers
253 views

Internal Representation of ?name and ??name

Code FullForm[Hold[?name]] Syntax::bktmcp: Expression "Hold[?name]]" has no closing "]". Syntax::sntxi: Incomplete expression; more input is needed . Question ...
4
votes
3answers
225 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?
1
vote
1answer
210 views

Can I use Table without the appropriate bounds?

I´d like to use the Table command without defining n, so that I can have a list of n ...
15
votes
2answers
449 views

Distributing PlusMinus consistently

I would like to give the built-in function PlusMinus, which is undefined by default, the intuitive meaning: considering all possible combinations of $+$ and $-$. ...
2
votes
4answers
523 views

Using the result of Solve in subsequent calculations

I'd like to know how to use the results of Solve in later calculations. Here's what I'm doing now: This is my expression ...
2
votes
1answer
912 views

Indices and variable definitions in Mathematica

Does anyone know how I can do this in Mathematica? Just an example.. Defining indices and variables (defined over indices), "mapping" variables and indices: ...
11
votes
2answers
278 views

Convert operator to string

How to programmatically convert an operator such as Equilibrium into its displayed form as a string? The conversion should work like this: ...
11
votes
3answers
272 views

Numbers in alternate bases transcend the evaluator?

It looks to me like a number in a base other than base 10 gets evaluated before the evaluator ever gets a chance to be tweaked. For example, FullForm[16^^abcdef] ...
7
votes
2answers
185 views

“A number in base b” and pure functions: why doesn't b^^# & work?

Why do the following not work (in Mathematica 7)? 2^^ # & /@ {1000, 1101} and 2^^ # & @ 1101 This does work: ...
2
votes
1answer
209 views

What is an alternative to using backticks in separating namespaces from function names?

What is an alternative to the backtick (`) in separating the namespace from the function name? Can the function be called without using this symbol? I think in ...
8
votes
1answer
437 views

Setting the DifferenceOrder Option

I've been playing around with Method in NDSolve[...] and can't quite seem to figure out how to force ...
4
votes
3answers
826 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)\, ...
8
votes
3answers
2k views

Using D to find a symbolic derivative

I need to do the following: Define a function Take the derivative of this function and have a look at the symoblic representation Substitute in some values With the bonus that I want to use the ...
5
votes
3answers
468 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?
7
votes
4answers
6k views

Mapping multiple parameters of a function to specific values

I am a little bit confused by the documentation for Apply (@@). I want to define a list of parameters, for instance: ...
1
vote
2answers
249 views

Finding the position of a specific value in a list

Is it possible to easily find the position of a specific value in a list? For example, if the list is {{x1,y1},{x2,y2},...,{xn,yn}} I would like to know the ...
5
votes
1answer
233 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. ...
10
votes
2answers
104 views

Functions in a different context are replaced with infix forms of their namesake in System`

So, in an attempt to help out Fabian with his question, I did what I often do, and created a new symbol in the Pillsy` package that I could play with. Since it was ...
1
vote
1answer
606 views

What does the slash-colon symbol do?

I came across a bit of code that uses the syntax /: and I don't know what it does. I can't find its documentation, or maybe I'm just not looking properly. The code ...
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 \\... ...
3
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
1answer
109 views

How do you set an Optional parameter with a global variable on a Function defined in a Package

In a Package I am writing, I'm trying to define a function with an Optional parameter in it that is set to a global variable. ...
9
votes
1answer
166 views

Accept Infinity as an Integer argument

I have the following function, albeit contrived: Foo[x_Integer] := Module[{i}, i = 1; While[i <= x && i <= 10, i++]; i - 1 ]; I am ...
8
votes
2answers
281 views

Cases[data,Colon[key,_]] vs. Cases[data,key:_] toward XPath, XQuery

Exploring methods to index and search tree-structured key:value pairs via named-entity index (key paths) as opposed to Position-based indexing. Using Rule as ...
3
votes
1answer
357 views

Explanation on why Compile statement works only if input and output sizes work

I found the following code: Compile[{{m, _Real, 2}}, Fourier[m]][Table[N[i - j], {i, 4}, {j, 4}]] which doesn't work correctly. But the following was posted as a ...
2
votes
2answers
2k views

NMinimize with defined function call getting error NMinimize::nnum

I want to call the NMinimize function for my own defined calculations but I got an error. Below is a simple example. ...
13
votes
7answers
945 views

Equating matrices (or higher order tensors) element-wise

Say I have two matrices (or, as in my case, higher order tensors) $A,B$, and I want to solve the equation $A=B$. To do so , I need a list of equations that equate entry-wise the elements of $A$ and ...
8
votes
4answers
672 views

Error when using rule as a list index - { i, x[[i]] } /. i -> 5

I can't seem to use a rule to index a vector. x = Range[10]; { i, x[[i]] } /. i -> 5 I get the following error when evaluating the above code, even if the ...
4
votes
3answers
335 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 ...
1
vote
1answer
159 views

Differentiation w/o assiging concrete values

v = Subscript[v, 0]*Sin[(Pi*S)/Subscript[S, 0]]; a = dv/ds v; a = D[v, s] returns ...
25
votes
1answer
484 views

Why doesn't PatternTest work with Composition?

While playing around with the solutions to this question, I've found some very strange behaviour: ...
3
votes
2answers
758 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 ...
3
votes
5answers
699 views

Using variables in function names

I want to make a list of plots and my functions are named C1, C2... Cn. The command I wish ...
5
votes
4answers
315 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, ...
13
votes
2answers
1k views

Representing second derivatives with a double overdot

I would like to express a second derivative with two dots above the variable. You can do this with a first derivative by saying: ...
9
votes
2answers
1k views

Flatten at a certain level

In an earlier question the brainteasing fourth syntax variant of Flatten was discussed. I see that with ...
12
votes
3answers
457 views

With versus Function

I've seen people compare Block with Module and With as scoping constructs, and try to figure ...
18
votes
5answers
639 views

Change syntax from other programs to mathematica syntax

Is there a good way to transform syntax from other computer algebra systems or from latex to mathematica syntax?