# Tagged Questions

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.

179 views

### Invalid Symbol Characters

What unicode characters are invalid as a Symbol name? Ideally I'm looking for a complete list. Here is the current list ...
42 views

### Evaluation of a Laplace transform for e^-at does not give expected results [closed]

LaplaceTransform[E^-at, t, s] That is my input, and the output I am expecting is 1/(a + s), but I am getting ...
108 views

### Multiple Constrained Sum

I need to perform a multiple summation, that obeys some conditions. This arises in the study of a statistical physics model. q=Exp[-β]. I would like to ask if ...
185 views

### Why is Reap result nested? [closed]

A minimal (toy) example for my question: i= 1; Reap[Do[Sow[i = (i + 1)^2], {4}]] (* {Null, {{4, 25, 676, 458329}}} *) I presume the entire result is a ...
147 views

### What kind of creature is h[c] for definition h[c_][x_] := (* function of x and c *)

To implement "Hero's Method" for approximating $\sqrt{c}$, one iterates the function (x + c/x)/2 for a given number c (e.g., <...
69 views

### Display a triangle that rotates at certain rate when space bar is held down?

This question is a follow up on: Open a pop up window that runs a calculation in loop until it is closed? How can I open a pop up to show a picture of a triangle that rotates by ...
87 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 ...
265 views

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### How to use MakeExpression in terminal?

This is in continuation to the question in Infix form of PutAppend ( >>> ) does not work with variable. I was trying to use ...
117 views

### Summation over list elements

As we know, one of the simplest way to do a summation (with special intervals) over list elements is using Sum[list[[i]], {i, 3, 8, 2 }] (*with steps of 2*) for ...
610 views

### When to use @@@ vs. /@ [duplicate]

So much thanks to Szabolcs in improving sequence.. for complete explanation. I am so glad to read all explanation which fundamentally remove the problem. But in number 4 of its explanation pointed to <...
330 views

### ToExpression processing errors

Is their a way to get a more comprehensive return value when running ToExpression? For example when I run ...
252 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 ...
99 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, ...
432 views

260 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) ...
67 views

### String option names for Cells

They seem to be correctly interpreted. I'm asking because of some minor reasons and a major one: NotebookWrite a Cell with WholeCellGroupOpener option I don't know any official confirmation so let ...
104 views

### Simplify set-theoretic expressions [duplicate]

As I can get set-theoretic simplifications of expressions and corresponding Venn diagram for example ...
41 views

### Mathematica Workflow [duplicate]

What methods/tools/tips have you found that dramatically improved your Mathematica workflow? I have a love/hate relationship with Mathematica. It is useful no doubt, but defies my intuition at every ...
118 views

### How to enter piecewise functions into Mathematica [closed]

I'm trying to enter a piecewise function (named eq30) into Mathematica. However, it seems not to work. The expression I entered is ...
54 views

### A question about the syntax [closed]

I have $3$ elementary questions to ask and I thank you in advance. Question N°1. What is the right syntax for $$y\equiv0\pmod {2}$$ in the code below? ...
185 views

### How to Write Partition with Infix?

The documentation says that using Infix ~, the following input f[e1,e2,e3,...] can be rewritten as ...
93 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 ...
69 views

### How to define an expression which is differently evaluated in calculations and printed

Let's say, we have a list: values = {1.2, 0.04, 0.9}; Is it possible to replace 0.04 by some expression, which displays as <...
129 views

### Can't get a plot from piecewise parametric function [closed]

I can't seem get a 3D plot from r[t]. Any suggestions? ...
138 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 ...
136 views

### What is the meaning of Range[10] /. {x_ /; PrimeQ[x] -> x^2}? [closed]

I'm currently doing a unit at university that touched briefly on Mathematica, but the final exam will feature multiple choice questions from Mathematica (along with excel and matlab). This leads to ...
199 views

### What is a good way to code long, complex, compilable algorithms?

The functional paradigm of the Wolfram Language used in Mathematica is all around wonderful. For intense numerics, Mathematica comes with the ability to Compile ...
109 views

### Mathematica and special functions

How is it possible that Mathematica doesn't recognize it's own definitions of special functions ? I tried as input: ...
81 views

### Failure in the use of FullSimplify

My question is about an apparent failure of the function "FullSimplify" to simplify an easy algebraic expression. This is the expression that I ask Mathematica to evaluate: ...
81 views

### Sign of a symbolic expression as a function of parameter values

I need to know the sign of the following expression for p[t] = z/(1-a), as a function of the parameters {a, b, c, z}: ...
144 views

### How to evaluate sum with different coefficient in each term?

I would like to know if there is a syntax that allows me to enter a sum that has coefficients that vary for every term? I have no interest in evaluating them numerically, but rather to keep them as ...
103 views

### Matrix with infinity on main diagonal

The question is trivial, however, there might be unexpected solutions. What would be nice way to create a square matrix with $\infty$ on main diagonal, and some arbitrary constant everywhere else? My ...
77 views

### how to manipulate indices in a table/vector

Perhaps I'm missing something very basic. Could somebody guide me how to manipulate indices of a list. For example, if I have ...
159 views

### GCD of Table entries

This question is from a newbie, so please be gentle in thrashing if I'm missing something very basic. How can I use GCD on a matrix/vector entries stored as Table. For example, if ...
46 views

### Treating expressions as symbols [duplicate]

I'm trying to do something like this: test = {x, y}; With[{test[[1]] = 3}, x/y] However, the following error is printed: With::lvset: "Local variable ...
54 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 ...
40 views

### Testing Conditions in For Loops

I am attempting to create a set of coefficients that satisfy a set of conditions using the Do function and If statements. I did this successfully with a basic set of conditions: ...
598 views

### Why aren't parentheses ( ) an expression in Mathematica?

Why aren't parentheses ( ) an expression in Mathematica? Can I get an expression in a form where parentheses are represented by an expression?
109 views

### Why are SetProperty and PropertyValue not working here?

I have a very simple graph, a loop: ...
89 views

### Why minimization does not work with symbolic array as arguments

If I try to minimize with constraints a function of several variables, with Gamma regularized function involved in the constraints it seems to works, as shown below (this is just a dummy example ...
77 views

### Negative accuracy numerics ( 0-128 notation )

What does it mean to have a negative accuracy number? I understand 0128 to mean "the number zero to 128 decimal points". Mathematica corroborates this: ...
95 views

### How to make sure input is an ODE

I'm having trouble wrapping my head around why this isn't an ordinary differential equation. ...
258 views

### How To Use D[ ] to Define a System of PDEs

We have two variables $u_{1}$ and $u_{2}$ which are functions of $x,t$. That is, $u_{1}=u_{1}(x,t)$ and $u_{2}=u_{2}(x,t)$. Consider the the system of partial differential equations \frac{\partial ...
52 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 ...
235 views

### Integrate using \[Esc] int \[Esc]

I like writing integrals symbolically instead of using Integrate[]. I suddenly seem to not be able to do this and am confused. I type \[Esc] int \[Esc] then ...
138 views

### Partial derivative of defined function with vector input

Background: Have written a formula for the refractive index for a glass slab (n) that depends on the variables t,a and d. Now I want to calculate for example some sort of error and I'll be needing to ...
What is the correct idiom for mapping the $0$ value in a modulo $n$ expression back to $n$. For example if I want to be sure that any integer value maps back to the index for a character in the ...