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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2
votes
2answers
128 views

Using a variable for two different purposes

I want to name a bunch of tables after the OEIS entries which describe them. Is there any way to use these names for both the table name and the link at the same time? The second line uses the ...
2
votes
3answers
240 views

Treat strings as variables?

I have a list of strings, {"x1", "x2", "x3", "x4"} And a list of linear equations: ...
16
votes
4answers
1k views

How to implement the Observer design pattern?

As a programmer with a history with procedural languages, the Observer design pattern inmediately springs to my mind when attacking certain class of problems, mostly UI/notifications related. A ...
2
votes
1answer
109 views

How to define a matrix with all elements 0? [closed]

A matrix can be defined as M = Array[m, {3, 3}] which gives ...
0
votes
0answers
88 views

Is there a better way of creating/assigning variables programmatically than using strings and ToExpression?

For quite a while now I've been wondering how to assign variables programmatically, and I have finally figured out one way of doing this. For example in a game where you have a variable number of ...
0
votes
0answers
31 views

How to change $n$ variables with $n$ Buttons automatically [duplicate]

I was trying to make a little game, and I came accross this problem. The goal is simple. There are going to be $n$ number of buttons, and each one will change a value of one variable. For example, ...
1
vote
1answer
41 views

How to set the values into some variables from different lists [closed]

I have a list of Values and a list of variables. I want to set the Values into Variables. Assume the following code: ...
0
votes
0answers
56 views

How to hide global variables in package?

in the package I'm writing I have a list of global variables which should not be visible from a notebook. Here's an extract of the package: ...
0
votes
3answers
148 views

Clean-up Code / Reduce variables

I'm writing a playing card simulator of sorts, and everything works fine, but some Modules use a disgusting amount of variables. For Example: ...
0
votes
0answers
35 views

Block, With, Module, can anyone help me understand the distinction? [duplicate]

I've been working heavily with Block[] for months in my research so I've read the documentation for the seemingly similar commands With[], Block[], and Module[]. Personally, I've had by far the ...
1
vote
0answers
59 views

Telling mathematica that something is an integer [duplicate]

Is it possible for me to tell mathematica something is an integer? like if I typed Sin[n Pi]+Cos[n Pi] it would tell me it equals 1 for even n and -1 for odd n? ...
0
votes
0answers
96 views

Local variable names - Is there an easy way?

I apologize first, because this has been asked, like in Treat all variables as local in a module [duplicate] Variable scope similar to other languages But I don't get how to use them. Some codes ...
7
votes
1answer
241 views

Defining my own invisible operator

There are some invisible operators in Mathematica (\[ImplicitPlus],\[InvisibleTimes],...
0
votes
2answers
158 views

setting real parameters in Hamiltonian matrix

The following Matrix represents my Hamiltonian. m = {{ B/2 - d - j/2 + a, (Sqrt[2]*j)/2, M}, {(Sqrt[2]*j)/2, B/2 + a, 0}, {M, 0, (-3*B)/2 - d + j/2 + a} How can ...
3
votes
2answers
141 views

Bare symbol invocation fails but not if used with an argument

How to achieve the following behavior on a symbol f? Background: The main goal is to use the symbol to tag an abstract data structure where downvalues are used to store information. Only defined ...
10
votes
2answers
313 views

How to take derivative of parameterized coordinate?

Suppose I have a vector in $\mathbb{R}^n$ but $n$ is not known in advance. I want to be able to write functions which operate on the components of that vector, and then I'd like to be able to take ...
0
votes
2answers
126 views

Define a function on a parameter argument set to zero

Say I have an expression (matrix) that depends on several variables. f= {{a, b+c},{2a-b^2,c^5+a b}} I want to define new matrices with the single parameter ...
0
votes
0answers
36 views

Varying number of function arguments [duplicate]

I have a function of six arguments: ffit[q1_, q2_, q3_, q4_, q5_, q6_] := (a1*q1^2 + a2*q2^2 + a3*q3^2 + a4*q4^2 + a5*q5^2 + a6*q6^2) ...
1
vote
0answers
67 views

Why the variable cannot use subscript? [duplicate]

Today,I use the Lagarange method to deduce the robot 's dynamic equation .I use the mma to help me calculate. I want to use $$x_B,y_B, v_{Bx}, v_{By}, v_B ^2$$ to represent the point B 's ...
0
votes
2answers
119 views
0
votes
1answer
79 views

Circumventing the default scoping: Assign a variable inside a function [duplicate]

I'm currently trying very hard to assign a variable inside a function. Therefore I'm using a function like this, which should reassign a predefined variable. ...
1
vote
1answer
163 views

Is linear interpolation applicable here

From my understanding about Linear Interpolation especially of that of Newton's Divided Difference Polynomial, we could get the value of F(x) from the given set of ...
6
votes
1answer
160 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 ...
20
votes
3answers
399 views

Why x = x doesn't cause an infinite loop, but f[x_] := f[x] does?

If I execute: In[1] := x = x Out[1] = x and then I evaluate the symbol x: ...
4
votes
1answer
177 views

Forcing Mathematica to recognize a symbol without defining it

In the Mathematica front-end, symbols that have been defined are colored black and symbols with no definition associated are colored blue. This is useful to prevent spelling mistakes. Also, defined ...
4
votes
1answer
198 views

What does it mean when a function is defined with two pairs of brackets

I have noticed a function defined as such: f[x_][y_] := expr; How is the argument y in 2nd pair of brackets being used? What is the difference from defining a ...
1
vote
1answer
193 views
1
vote
1answer
86 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}] ...
10
votes
4answers
606 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 ...
0
votes
0answers
112 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
149 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 ...
3
votes
3answers
119 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
37 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
132 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
77 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
348 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
88 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
174 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 ...
2
votes
5answers
219 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
1k 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 ...
1
vote
3answers
120 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 ...
5
votes
4answers
489 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
105 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
214 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
493 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 -- ...
8
votes
3answers
172 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 ...
19
votes
2answers
338 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
205 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 ...
13
votes
3answers
376 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 ...
2
votes
1answer
116 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: ...