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.
219
questions
2
votes
1answer
40 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 ...
4
votes
4answers
239 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}
...
0
votes
2answers
76 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:
...
0
votes
0answers
45 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 ...
0
votes
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:
...
0
votes
0answers
31 views
ReplaceAll Not Working Correctly
I'm trying to use replaceall to redefine my expression in terms of a separate variable..
...
0
votes
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. ...
1
vote
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 ...
0
votes
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 ...
0
votes
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
...
0
votes
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
...
3
votes
2answers
83 views
4
votes
1answer
46 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 $2^n \times 2^n$....
0
votes
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:
...
5
votes
3answers
455 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]
...
3
votes
1answer
493 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).
...
5
votes
1answer
88 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. ...
0
votes
0answers
33 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 ...
2
votes
1answer
73 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 ...
0
votes
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 <...
0
votes
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 ...
1
vote
2answers
55 views
0
votes
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:
...
1
vote
1answer
44 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 ...
0
votes
0answers
32 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
...
2
votes
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 ...
1
vote
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]
...
1
vote
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.:
...
0
votes
2answers
70 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 ...
1
vote
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 ...
1
vote
1answer
50 views
Rearranging similar terms in an equation
In a piece of code I am writing, I run into an equation of the form
...
0
votes
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
0
votes
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 = ...
4
votes
1answer
249 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 ...
0
votes
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 ...
0
votes
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]
...
0
votes
1answer
132 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 ...
0
votes
1answer
78 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. ...
0
votes
1answer
53 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
...
0
votes
1answer
41 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:
<...
1
vote
1answer
157 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 ...
1
vote
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
votes
2answers
80 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
votes
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]
...
2
votes
2answers
98 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:
...
1
vote
2answers
61 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 ...
0
votes
1answer
26 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
...
1
vote
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 ...
17
votes
2answers
341 views
When to name a variable with $
There are some symbols in the Wolfram Language that start with $, including $Abort, ...
1
vote
1answer
58 views
Mathematica is picking up variable definition from other files
Mathematica is using definitions from other open files in the same folder.
I want variables not defined in a particular file to be treated as undefined variables. I do not want Mathematica to pick ...
