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

7
votes
2answers
366 views

What's the purpose of the Unique function?

As the title says: What's the purpose of Unique? I understand that it generates some unique symbol, but when and for what is it to be used? Are there applications ...
5
votes
4answers
365 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 <...
4
votes
0answers
93 views

Why does FromDigits transpose its argument (sometimes)?

a = {{1, 2}, {3, 4}, {5, 6}} ; FromDigits /@ Transpose@ a == FromDigits @ a (* True *) The only "strange" syntax I've found in the docs is But it doesn't ...
3
votes
0answers
516 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, ...
3
votes
2answers
130 views

Substitution in parameters to “Which”

Why in this expression ...
3
votes
1answer
381 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 ...
3
votes
1answer
100 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: ...
3
votes
1answer
83 views

Open a pop up window that runs a calculation in loop until it is closed?

How should I construct a code which opens a pop up window, displays a constantly updating image in it and is terminated once the pop up is closed? The constant updating would be an infinite loop of ...
2
votes
1answer
88 views

RegionUnion issues with many Regions

The new RegionUnion[] function is just what I needed if only I could get it to work. I have many non-overlapping regions that I will need to use as plotting domains ...
2
votes
2answers
375 views

local variable naming & symbolic argument

I'm stuck here with my variable assignment in this scenario ...
2
votes
4answers
142 views

How to obtain the gradient of a function as a function?

The Grad function allows me to get the gradient of a function like this: ...
1
vote
1answer
94 views

Cannot use Part in Pure Function [duplicate]

I need to select some lists in the nested list of form of {{1,2,3},{2,3,4}}. I have used Select to complete my work. But when I tried Position, it doesn't work. For example, ...
1
vote
0answers
79 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 ...
1
vote
1answer
557 views

Why is Euler's number an uppercase “E” and not a lowercase “e”?

Why is Euler's number an uppercase "E" and not a lowercase "e"? Isn't Euler's Number normally expressed with a lowercase "e"?
1
vote
1answer
154 views

How would one minimize with respect to an unknown number of variables?

Say I had a function like the following: f[n_] := Sum[a + Subscript[b, k], {k, 0, n}] Such that ...
1
vote
1answer
52 views

Using the Nest function — Confusion on my output

I have the following code and output where the original function is $f(x,a) = a^2 - x^2$. ...
1
vote
1answer
271 views

Syntax error: newline character interpreted as multiplication

I'm getting this error in Wolfram Workbench, and I don't know where it comes from: "Syntax error: newline character interpreted as multiplication" This error happens around an If[] function, in a ...
1
vote
1answer
446 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 ...
1
vote
1answer
110 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 ...
1
vote
1answer
78 views

Ways to protect certain parts of expressions

I am currently working on a quantum mechanics problem where I try to find equations that relate different states of a many-body system. The states are described by sets of pairs of integers, like <...
1
vote
1answer
137 views

How to make a StreamPlot with three variables and two expressions

I'm trying to make a StreamPlot in Mathematica with three variables. I already have two variables, x and y, that make an ellipse via StreamPlot[{-y,x}] but I ...