# Tagged Questions

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.

103 views

### How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc

I'm trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuff like that. When I say, for example, ...
24 views

### Variable as Difference of 2 Variables

I would like to evaluate a function based on the absolute difference of two variables. An example: g=5*x-5*x*y-5*y diff=x-y D[g,x] D[g,y] D[g,diff] I cannot find ...
45 views

### Defining a function that prints both the name and value of a variable defined locally within the calling function

To save time when debugging with Print statements, I'd like to define a function -- call it PrintVal -- that prints both the name and value of a variable defined locally within the calling function. ...
72 views

### How to form a variable from matrix elements

I have matrix with n rows and 2 columns, say m = {{x11, y12}, {x21, y22}, ..., {xn1, yn2}. Now, I want to form three new variables for example: ...
90 views

### How to create a complex variable from dated list values

Can anyone help me to construct a variable "PI" from values of variable x. Variable x represents a group of two time series rj and ri on equal dates(joined two dated lists with states).Variable x have ...
61 views

### Equivalent command to the Maple indets command

This carries on the discussion here and here. I had mistaken Variable[] to give you ALL variables in an expression, but apparently, it is not meant for that. ...
71 views

I do believe this sort of similar questions had been asked many times, so I have read a LOT. For example this and this as well as many other related posts. But a glance at what my main question is ...
72 views

### Need some explanation of “Global*”

When I start a new notebook, I enter Names["Global*"] I get this {"list", "msgs", "rhs", "z"} Then I enter, ...
14 views

### SharedVariable in WebMathematica

How can I create a variable to be used and setted over all my WebMathematica kernels? Here is the case: Create a package with do data structure like: data = ...
110 views

### Variable Value as Range

Thank you for the help so far! I would like to assign +/i signs for the function and solution such as (+)(+)(-) and therefore (-). It is working for the first evaluation, λlower, but not for the ...
124 views

### Convert matrix rows into variables

Can anyone show me how to set all matrix rows to variables. For example, I have matrix w={{1,2,3},{3,2,1},{0,0,0}} and I need to set each matrix row to be separate ...
39 views

### Replacing variable names in a notebook

I am working on a code that simply imports and graphs a function. If I preset the directory I would have something that looks like this: ...
129 views

### Assign output of solve to variables [duplicate]

I have this input: Solve[x^2 + 3 x + 2 == 0, x] which gives this output: {{x -> -2}, {x -> -1}} I want the first x ...
286 views

### Is garbage collection broken in version 10.0.0?

Bug introduced in 10.0.0 and fixed in 10.0.1 In version 10.0.0 under Windows I am observing the following behavior: ...
90 views

### Local variables whose definitions depend on each other [duplicate]

Consider the following (pseudo-)function definition: f[l_] := Let[{ a = Length[l], b = First[l], c = b/a, }, c*10] So for ...
74 views

### Store matched variables

Edit: I am matching and replacing a particular expression. At the same time... I want to store matched variables for later use. I got it to work with messed up code involving ...
92 views

### Solving equations with QuantityVariable

I'm trying to understand how to easily solve equations that use QuantityVariable. Why does this fail? ...
31 views

### Why would this function work only when I make a copy of the variable? [duplicate]

Why would this function work with a copy of the function variable: ...
101 views

### How to name a variable with the value of another variable?

A simple but very important (at least for me) question. In some languages for defining a variable, for example, we can do: i=10 "d"&i=30 So I have defined the variable d10, and... d10=30 ...
36 views

### Reducing Output length by introducing new variables [duplicate]

I have outputs like "expression/(1+3*c^2) +anotherexpression/(1+3*c^2)" and so on. Is there any way to set 1/(1+3*c^2)=A where A is a new variable so that the output reads like ...
60 views

### specifying a list (vector) of arbitrary length

When trying to do symbolic calculations in mathematica involving a space of dimension n, which is arbitrary but fixed, I'd often like to work with vectors that have ...
76 views

### How do I constrain variables to a user-defined domain in ArgMax?

I am trying to ArgMax a function over x, but x is only defined between ...
1k views

### Best practice of passing a large number of parameters to functions

I have a number of functions that all take a large number of parameters. I am wondering what is the best practice of passing these parameters to those functions. I could, of course, simply specify ...
56 views

### Is there a command returning information about a particular object? [closed]

Suppose I have a variable var1, a function MyFunction, and a graphic SomePlot. I remember ...
121 views

### Multiple down-values with exactly the same lefthand side

I was working on an answer to this question, when I was sidetracked by what I bring up here. I wanted a function, which when given a string representing a binary number, would convert the string to a ...
49 views

### Coupled ODEs with boundary conditions - DSolve Error

I'm relatively new to mathematica and I can't find the error here. I suspect it has something to do with the fact that vx, vy, vz aren't blue on my mathematica - as in, they already have some assigned ...
88 views

### Using AddTo in a function

I want to create a function that will take a variable $x$ and reassign the value $x+2$ to $x$. So f[x_]:= x += 2 However: ...
105 views

### Identifying the symbol which has a specific value

I'm writing a program that will solve the value of 1 variable in a 4-variable equality equation, but the variable to be solved will depend on the user's input to the program. This is what I've come ...
72 views

### Calling variables with use of numbers in their names

I have got few huge matrices named by ascending numbers, e.g. x1, x2, x3,... and I need to do the same operation with all of them - to multiply their components, ...
113 views

### Extract memoized results in the form of a rule

Lets say I define a function f with memoization. Is there some way to extract the memoized values? For example, ...
121 views

### Define function that counts recursive fibonacci

If I write count=0; fib[0]:=(count=count+1; 0); fib[1]:=(count=count+1; 1); fib[n_] := (count = count+1; fib[n-2] + fib[n-1]); Then I can ...
126 views

### Define the square of a function [closed]

Is there any good way to define the square of a function in M9? Usually one can write e.g. f[z_] = 3*Sin[z] etc etc. But is it possible to define ...
31 views

### Indexed variable with alternatives

I have a["tree"] := "oak" a["flower"] := "rose" a["dog" | "cat"] := "animals" I want that the last definition of a behaves ...
63 views

### How I can define a new function as a function argument?

I need to pass a function with t as independent variable as a function parameter and want to create a new function of the same through this provided the argument of another function. Here is my code. ...
36 views

### Can the value of a variable be made to persist between front end sessions? [duplicate]

For example, say I create a notebook with a cell a = 5 + 2 and then I close Mathematica, reopen the notebook, enter a new cell ...
88 views

### How to localize symbols on the right-hand side of Rule when using ReplaceAll?

I am frustrated by the following: {1, 2, 3.0} /. a_Integer -> a + 1 The a on the left side of the arrow is localized and ...
133 views

### When to use indexed variables

Still learning the fundamentals of the language I would like to ask you what advantages there might be in writing something like: a[1] = 2; a[2] = 4; a[3] = "x"; ...
46 views

### Quoting definition explicitly

I'm trying to quote a definition using DownValues, OwnValues, etc. Everything seems to be fine, except for temporary symbols' ...
46 views

### how to define roots of an equation as a function? [closed]

I need to solve an equation depending on 3variables in only one variables and define the roots as a function of the remaining variables? I used some thing like that: ...
26 views

### Get value for a variable from user inside a module [duplicate]

I am writing a module. When I run the module, I want it to ask for a variable, like I can in other programing languages such as C++ or Python. For example, in C++: ...
69 views

### Maximum number of literal values for SetDelayed?

Under what circumstances should I expect Mathematica to turn a delayed assignment into an immediate assignment? I have put together a minimal example (available here) which demonstrates this behavior. ...
127 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 ...
235 views

### Treat strings as variables?

I have a list of strings, {"x1", "x2", "x3", "x4"} And a list of linear equations: ...
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 ...
99 views

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

A matrix can be defined as M = Array[m, {3, 3}] which gives ...
81 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 ...
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, ...
40 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: ...