Questions on assigning and unassigning definitions to names that represent them, including issues raised by context and localization. Use tag [assignment] for issues relating to Set versus SetDelayed.

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1
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1answer
114 views
10
votes
4answers
394 views

Refering to global variables inside modules

How do I refer to global variables inside modules if the same name is used for a local one? In code, I want that ...
1
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1answer
82 views

Plotting with multiple variables [closed]

What is the simplest way of plotting across multiple variables? eg: I would like to plot something like this: Plot[{x^0,x^1,x^2,x^3,x^4,x^5,x^6}, {x, 0, 10}] ...
3
votes
3answers
107 views

Using a variable to tell Mathematica which existing variable to manipulate

I have an estimation routine I have coded up, I want now to do some tests on it where I pick a particular parameter and run the estimation for differing values of that parameter. What I want is to be ...
0
votes
0answers
87 views

NIntegrate with an arbitrary number of variables [duplicate]

I need to evaluate NIntegrate with a variable number of variables. Here's a concrete example. I'll accept an answer that finds a way to make the example work. I ...
3
votes
2answers
117 views

Assigning an equation as a variable

I am compiling a calculator where many slider parameters are used to define a value, where the defined value may then be reused to define another value. I am unable able to, or at least been ...
20
votes
5answers
2k views

Clear complains that a subscripted variable is not a symbol or a string?

Here's a small listing where I've used EscqEsc to typeset θ in the notebook: ...
0
votes
0answers
36 views

Subscripts to a variable; why a letter shoud come before a digit?

I noticed that I cannot create a variable $f_{2s}$ since Mathematica seems to leave a space between the subscripts 2 and s ...
1
vote
2answers
121 views

Add a letter to a variable name from a list

Basically I am searching for a way to add the letter u to an existing list of variables {a,b,c,d} to obtain the variable list ...
0
votes
1answer
64 views

Collecting variables from Subscript

I have followings set: t = Transpose[{x[#] & /@ Range[20], RandomInteger[15, 20]}]; Subscript[#[[1]], #[[2]]] & /@ t The code is just to build my set.So ...
2
votes
2answers
184 views

Table of Variables

I use a list of variables {x1, x2, x3} to Solve a particular set of equations. I am now trying to generalise this depending on ...
2
votes
1answer
82 views

What is the need for function parameters? Many possible inputs

If I have many possible variables related to one another, why do I need to define my function with parameters for plotting? For example, if I have an equation like: ...
3
votes
1answer
123 views

Define a function with the condition that it must be positive

I have a function f(x) and I want to define a new function g(x) that is equal to f(x) only ...
5
votes
4answers
421 views

Why do I see the error “only assignments to symbols are allowed” when using a Module and not otherwise?

When I type Remove["Global`*"] foo[] := Module[{Subscript[a, 1] = "x"}, 0]; foo[] I get the expected error "only assignments to symbols are allowed". I ...
2
votes
5answers
201 views

Treat list as cyclic

I am considering the following case. Say that T={p1,p2,p3} represents a triangle. In addition, I want to parameterize the edges of the triangle ...
1
vote
0answers
649 views

How to assign (and retrieve) variables with subscripts? [duplicate]

I like to give subscripts to my variable names when the variables are related. I.e., Subscript[r, i] = 3 3 A problem arises when I later assign ...
12
votes
5answers
1k views

Define a mathematical set

I have a terribly short question: Is there a way to define a pure mathematical set? I tried a bit of googling, but the word "set" has two meanings and the other one (as in setting) as by far more ...
1
vote
3answers
107 views

Declare local variable when defining a function to mimic Table[]

The problem: I want to define a function tab to replace the long line Table[f[i,j,k,l],{i,3},{j,3},{k,3},{l,3}] by a shorter ...
2
votes
3answers
290 views

How can I prevent Superscript from being interpreted as Power?

I have very strong desire to use superscript as the index of the variable. However, it looks like that the Mathematica automatically recognize the superscript as the power and I got message that my ...
2
votes
2answers
95 views

Extracting variables from Hold expression

For example I have some global assignments x=1;y=2;z=3 and an expression Hold[x*y/z]. How can I now extract variables ...
3
votes
2answers
175 views

How to declare a function that uses local variables of a module outside this module?

I have the following code Module[{f,x=0}, f[t_] := x + t; ..........; ...f[1]...; ..........; ] My aim is to put the declaration of the function ...
6
votes
2answers
293 views

Obtaining the name of a variable as a string [duplicate]

Suppose that I have an arbitrary variable myVariable. Is there some function fun -- either built-in or one that I can define -- ...
2
votes
1answer
99 views

Reuse local variable in declaration within With [duplicate]

Considering the richness of Mathematica.SE, I am quite surprised I could not find my answer... I am very sorry if it is a duplicate. Consider the following example: ...
-2
votes
2answers
179 views

Mathematica not assigning variable correctly

So I have been fiddling with this the last hour and I just can't get it to work. I have 3 matrices of the same size which contain nothing but 0's in a list, I also have 3 matrices of the same size ...
8
votes
3answers
151 views

Protecting function definitions only for particular inputs

I would like to be able to define the values of a particular function for new inputs. f[x1]=f1; f[x2]=f2; I would also like to be able redefine the values for ...
18
votes
2answers
316 views

The dangers of SaveDefinitions — should this really happen?

I have been bitten hard by SaveDefinitions -> True. I'll describe in detail what happened below. My questions are: Is this a bug? What is the most convenient ...
1
vote
1answer
149 views

Print indexed (by subscript) variable name systematically

I have some variables : Subscript[S, 1], Subscript[S, 2]...etc. But they are defined in a for loop like For[g = 1, g < 4, g++, Subscript[S, g] = g]; Later, I ...
12
votes
3answers
287 views

Variable scope similar to other languages

Mathematica, unlike many other languages, defines the variables in the global scope unless it is explicitly asked to define a variable in a local scope, e.g., using ...
3
votes
1answer
228 views

Evaluating a function on permutations of its arguments

Say I have a function "temp" of $n+1$ variables, $y,z1,z2,z3,...,zn$. I want to test if my function has certain symmetries like swapping $y$ with square of any $z$, swapping any two of the zs, ...
0
votes
1answer
92 views

Arbitrary number of variables in Module, Block, etc

How do I specify an arbitrary number of variable names and initialize them inside of a Module or Block? For example, I want to do something like: ...
0
votes
0answers
108 views

How to define a variable as a function of another variable?

I want to define a variable q which is a function of t. And I want to define another variable ...
1
vote
0answers
110 views

Variable scope in nested NMaximize, NMaxValue

I'm trying to use NMaxValue inside other statements (FindRoot and NMinimize). Those statements should bind variable names, but I'm getting weird warnings which seem to indicate that the variables ...
7
votes
1answer
141 views

Specifying optional arguments with variables

Perhaps this is poor programming on my part, but I would like to create a function that uses a variable as an optional parameter: var = 2; f[a_:var] := {a} The ...
3
votes
3answers
164 views

Renaming a list with name obtained interactively

I have a list say: m = {1, 2, 3} The list is inside a package, and is the result of a calculation. I want to give the user the option to rename it, for example ...
1
vote
3answers
318 views

Adding subscripts to variables

I know I can define vars = Map[Subscript[x, #1] &, {"tem", "pressure", "hum", "lat", "alt", "space", "corner"}] and ...
7
votes
6answers
576 views

Using a built-in symbol as a variable

I want to produce a Mathematica Computable Document in which N appears as a variable in my formulae. But N is a reserved word in ...
5
votes
1answer
270 views

Proper use of arbitrary number of variables

So, I'm working on a project where the number of independent variables is not fixed. Consider a problem of $N$ independent variables, $\boldsymbol{r}$. I want to perform different things with them. ...
8
votes
1answer
120 views

Is it possible to use the global definition of a symbol as part of its new local definition set in a Block?

Consider the following expression: Block[{Print = CopyToClipboard}, doSomething[]] Now all calls to Print from ...
16
votes
3answers
633 views

Create an adaptive amount of local variables for error propagation

I intend to write a function which calculates the result and the error for any formula with any amount of variables using the Gauß Error Propagation. The error $\mathrm{d}R$ for a function $R(a,b,c)$ ...
1
vote
1answer
523 views

How to linearize an expression automatically?

I would like to automatically linearize some long equations in the scope of variational calculus. Here follows an example of what I need to do : Given two variables $a_1 = q_1 + \delta q_1$ and $a_2 ...
1
vote
2answers
188 views

TabView: Reset some dynamic variable on tab selection

Given a TabView panel like this one TabView[{ DynamicModule[{x = False}, {Checkbox[Dynamic[x]], Dynamic[x]}], "foo"}] I ...
8
votes
2answers
212 views

Distribute and analyze large datasets

I need to analyze very large datasets, and they obviously don't fit in a computer memory. I need to produce some statistics on these datasets, and this brings me here: How can I make some statistical ...
5
votes
0answers
134 views

Context “Unique to This Notebook” makes variables black even if they're not defined?

I'm trying to use this technique to keep variables separated between different notebooks. It seems to be working fine, except that variables turn black as soon as they are evaluated — any ideas why ...
8
votes
1answer
151 views

Different behaviours of Default Argument

I don't really understand the behaviour of Default Argument. If I execute this command in Mathematica: In: {f[a], f[a + b]} /. f[x_ + y_.] -> p[x, y] ...
4
votes
3answers
621 views

How to Clear variables with apostrophe?

An apostrophe ' is often used when we want to distinguish two variables. For example, if we already have a variable t and we may ...
13
votes
1answer
583 views

What is $ sign in Mathematica?

Is it a special sign or it can be used as anything else? For creating variables for example. $x=4
3
votes
2answers
240 views

Mathematica does not understand (R^3)^(1/3) is the same as R [closed]

In the output from a calculation in mathematica stands a/((R^3*c)^(1/3)), with c and a ...
4
votes
4answers
147 views

Put local variables for Block in a variable [duplicate]

Is is possible to assign {x = 2, y = 3, z = 4} to a variable var so that one can write ...
1
vote
1answer
196 views

Generating a list of symbolic coefficients [duplicate]

I am trying to do something which I assume should be very simple: I want to generate a list with symbolic coefficients that looks like this: ...