Questions tagged [variable]

Questions on the use or manipulation of Mathematica variables (i.e. names associated with a changeable value). Use [variable-definitions] or [assignment] for questions on variable context localization, or assignment.

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56 views

Function and variables [closed]

Make a function in which for entered functions with 3 variables , values of variables and relative error of function ,calculates needed relative errors of variables. Can someone give me an idea how ...
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1answer
61 views

separation of variables in case of vector components

I have a function f in two variables y and theta, where y=z^2+x^2. There are numerical values for x,z,and theta ( x and z are the dimensions),I have to do calculations to obtain the velocity, so I ...
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1answer
45 views

Store boolean expression into a variable

My purpose is to use a boolean expression as a requirement that a pattern must comply. The requirement is c1 == "a", and I am using it to select a string from a ...
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4answers
241 views

Name a list with Table

I am struggling to find a way to assign a value from a list to names from another pre-defined list with Table[]. names = {first, second, third} ...
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2answers
77 views

Use Alphabet[] as a variable in a function

I'm trying to figure out if I can use the letters contained in Alphabet[] as variables for a function. As a simplified example, I'd like to do something like: ...
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0answers
49 views

Variables for multiple data files plotting using same Mathematica notebook

I am not an expert in mathematica, I have this following code. As you see I import a text file under the name "MyPoint1", plot with "pAll" then I do some more calculation with more variables and ...
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1answer
31 views

Reading and re-assigning variable

I am trying to create a table by iteratively calculating its values using a temporary variable accu: ...
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0answers
31 views

ReplaceAll Not Working Correctly

I'm trying to use replaceall to redefine my expression in terms of a separate variable.. ...
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0answers
35 views

How to restrict the use of variables to the notebook? [duplicate]

I am solving two problems simultaneously in which the variable x is defined. To the left of the image, i'm solving shape functions and matrix operations. But to the right i'm solving Green's function. ...
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3answers
42 views

Redefine function after change of coordinates (variables)

I wish to define functions of (possibly) several variables and then apply variable transformations in order to obtain a more comfortable expression. But I run into trouble because I need to redefine ...
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1answer
33 views

Extract variables from sum of unevaluted functions

I have sums of the form sum = a f[1,1,0] + b f[1,2,0] + c f[1,2,1] + ... It is always linear in f[a,b,c]. I would like a ...
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1answer
45 views

Reversing the flow of the equation sign. Compacting an equation. Choosing which variables to show

Here's a simple example of what I'm trying to get at with that mysterious title. I start off with a Hermitian matrix that I derived analytically ...
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1answer
36 views

remove one of the column in the output of Solve command

I would like to remove one variable in the output of the "Solve" command without changing the rest. For instance, in the following code ...
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2answers
84 views

From f[g[x,t]] to f[g]

How can you change f[g[x,t],t] to f[g,t] ? I have differential equations ...
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1answer
47 views

Computing Higher Order Tensor of Variable Rank

The following code takes a vector x of variable length, computes the outer product of the vector with itself to form the matrix $\rho$ of dimension $2^n \times 2^n$....
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1answer
35 views

Functions with Variable Numbers of Arguments: Outer Vector Product

I am trying to write a function that takes a column vector of variable dimension as an input and returns the outer product matrix as an output. What I have tried: ...
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3answers
456 views

How to transform a function from f[#1] to f[x]

So I have this function : Sqrt[-1 + Tanh[#1 - #2]^2] & How can I transform it into f[x_,y_]=Sqrt[-1 + Tanh[x - y]^2] ...
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1answer
516 views

General::ivar 0 is not a valid variable when using Series in Plot

I have been having some trouble graphing a Taylor series approximation (Series). ...
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1answer
89 views

Make assumption for function with variable argument

I would like to assume that a>t[b_] for any b, such that e.g. Simplify[a>t[c]]==True. ...
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0answers
34 views

Saving variable inside Manipulate command

I have been working in a plotter using "manipulate", I let the code below. However, I would like change between different kind of "options" that I will add them after, the problem is when I change to ...
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1answer
74 views

How to read in and assign values from a txt file?

I have a text file that I would like to import into Mathematica - after searching around the internet, I can't seem to find any pages that explain how to do this: The text file containes these four ...
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1answer
66 views

Table and FindRoot of a 2 variable function of x and t : cos(x + 3t)

I am trying implement mathematica commands: Table and FindRoot, of a 2 variable function <...
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0answers
87 views

Problem with fitting

So I have a very simple question related to a simple topic, but also directly related to a fitting problem. I see that my question is related to this question but I don't manage to make the bridge ...
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2answers
55 views
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1answer
59 views

Five equations to solve 6-variables question, is it possible?

I was given a task to find the value of variable a,b,c,d,e and f. But I'm not sure it is even possible, given that only 5 equations are available. Can anybody point out how to solve these: ...
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1answer
47 views

How to use a table with two variables as the values for a function with two variables (x and y)? [duplicate]

I'm sorry if this is a dumb question. I am a student and have 0 prior experience with Mathematica or any sort of coding and I have looked at various resources trying to figure it out myself but still ...
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33 views

Bounding Solve results to named variables

How can i bound results of my Solve function to variables properly? This metod works but causes unexpected troubles i struggle to resolve ...
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1answer
131 views

How do I create a variable that uses I?

I'm planning on working with a set of non-linear differential equations. A few of the equations look like: Mathematica tells me that I is protected. Is there any ...
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3answers
34 views

Simple question about variables into functions

Im trying to write a very simple code that will solve an equation. total = 800; side1 = x; side2 = total - 2 x; f[x_] := side1*side2 f[x] f'[x] Solve[f'[x]==0] ...
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1answer
26 views

How to define a function, that generates matrix of variables, which can be later used in Reduce?

My goal is to generate matrices, on which I will put different constraints in Reduce funcion, e.g.: ...
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2answers
71 views

Separating variables in a set of equations

I have a very large set of equations eqs with variables denoted by capital letters like PVA[2], QA[2], etc. and small letters like ica[1,2], tr[2,3] etc. And I have ...
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1answer
47 views

Apply different PlotStyles to functions with functions as variable [closed]

I have a function func[expr,var] with which I want to plot the list expr[var] and have different styles applied to it. When ...
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1answer
52 views

Rearranging similar terms in an equation

In a piece of code I am writing, I run into an equation of the form ...
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2answers
53 views

How to show the answer in terms of another variable

if we have A = 1; B = 44 + 1 output :: B = 45 how we can show B like this output :: B = 44 + A
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1answer
49 views

Changing variables to obtain derivatives of new variables [duplicate]

Let's say that I have some symbolic expression of a function $x(t)$, and would like to obtain its derivative $x'(t)$. However, I also have the following two identities, $\xi = \omega t$, and $\eta = ...
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1answer
250 views

Why is DSolve different when the equation is built programmatically?

Here is a simple differential equation. mwe=y[x]/.First@DSolve [{y'[x]==x-2*x*y[x],y[0]==0},y[x],x] I get the answer $\frac{1}{2}-\frac{e^{-x^2}}{2}$ If I build ...
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1answer
59 views

Why is ww[[1]] not a valid variable in FindMinValue and Plot [closed]

Why is ww[[1]] not a valid variable when given to FindMinValue and Plot, but is a variable ...
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0answers
27 views

How can I access the name of a variable inside a function? [duplicate]

How can I access the name of a variable inside a function? For example I have variables mike={some stuff} jenny={other stuff} and want to write a function f giving the following: input> f[mike] ...
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1answer
133 views

Can I bake my own PI using your Wolfram language oven and prebuilt utensils? [closed]

How might I override the value of the Greek letter PI within various builtin language functions in the Wolfram language? Specifically and without having to reinvent the wheel or code equivalent ...
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1answer
80 views

Computing an integral : Mathematica seems to say it's diverging or not defined and I think it is

I would like to compute : Element[a, Integers] Element[b, Integers] Integrate[Exp[-a^2*(x (1 - x/b^2))^2], {x, 0, Infinity}] which is obviously not diverging. ...
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1answer
55 views

Inequality with assumptions

I would like to find 2D region formed by $(a,c) \in \mathbb{R}^2$ such that the inequality $f(a,c,x,y) \geq 0$ holds for all $x,y \in [0,1]$. If I solve this inequality with reduce of the form ...
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1answer
45 views

Factoring out a parameter

I have some function: f[a_,b_,c_]:=Sqrt[a^2+b^2+c^2] Is there a way that I can factor out parameter (variable) b like this: <...
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1answer
175 views

What is the recommended way to plot a function with a dependent variable?

I am currently learning the basics of Mathematica. I can't seem to find a straightforward answer in the Wolfram documentation, probably for a lack of clarity in my queries. For example, I want to ...
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1answer
55 views

Question about ListPlot of variables [closed]

My question is trivial but I don't seem to be able to get the answer. Suppose that I do a numerical computation (division of some numbers that come from the numerical solution of an NDSolve or ...
3
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2answers
82 views

Using Symbolize to Convert Multiple Variables at Once

So, I have created a list of subscripted and overdotted variables that I would like to symbolize, so I run them through a for loop. Seems to me that this would work? Any help is appreciated. ...
6
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0answers
63 views

Nested rules and automatic renaming of variables [duplicate]

I understand why $ happens here: ClearAll[foo] foo[a_] := (x_ :> a x) foo[1] ...
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2answers
99 views

Possible to solve this function?

I have this function: Emax[T_, d_] := -(1/2) + d + d/(-1 + E^(d/T)) - 1/2 Coth[1/(2 T)]; All I want is to transform this Function so I get: ...
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2answers
64 views

Showing variable values on a 3D Plot

I am running a 3D plot a 100 times to show the dynamics of two undetermined variables (cM and cR) for a 100 values of ...
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1answer
29 views

Extract and name PNG's from loops [duplicate]

I want to extract PNG files and name them depending on the dummy variable of a loop. For example, starting from ...
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1answer
38 views

Use Solve for two Functions to find 1 common Variable

I have 2 functions that look like this: F[t_,d_]:= 10+t+2d G[t_,d_]:= 5+t+d I'd like to solve this in such a way to know for which t both Function have the Same value. I assume that this won't be ...

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