# 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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### How to plot the perimeter of an ellipse where the variable is its eccentricity?

I'm basically just trying to plot a function where the x value is the eccentricity of an ellipse and the y value its perimeter. I've tried first defining the eccentricity ...
1 vote
94 views

### Replacement rule for functions of two variables

In Mathematica when I use the substitutions rule (/.) If I have two variables {NN,H} each variables has 5 values and i want to substitute about the first variable ...
60 views

### How to define prefix that can turn numeric?

I put these prefix in my init.m file. First I Unprotect all these symbols, set values and then ...
1 vote
100 views

### Solving for linear combination of variables

I have a set of constraints on nine variables, ...
840 views

### List of letters longer than the alphabet

I would like to create a list of the first $n$ letters of the english alphabet. Importantly, I would like that in case $n$ is bigger than the size of the alphabet, the letters will start repeating in ...
76 views

### How to convert mathematica root expression to readable one? [duplicate]

I am trying to find out at what regions a function is monotonically decreasing. The function is a function of X and has two more variables epsilon and B with the constrains 0 < B, 0 <epsilon< ...
67 views

### Cannot Optimize where NSolve and NDSolveValue are involved with Multi-Variables

My Objective Function is Sqrt[Sum[((sol[[j]])^2), {j, 1, noofnode}]/noofnode] with variables v1, v2, v3, v4, v5, v6. But just ...
77 views

### How to change the values of a parameter within the domain in NDSolveValue?

In the following code, e is constant within the domain. But I want to change the value of e continuously within the domain. For ...
95 views

### How to Optimize a Finite Element Model with Multiple Variables in Mathematica?

Urgent Help, Please !!! I am attaching my codes for a Finite Element Model which needs to be optimized and the Objective Function ("of" in the code) has been mentioned at the last line of ...
91 views

### Help with Error: Recursion depth of 1024 exceeded during evaluation

I am quite new to Mathematica. Please excuse my mistakes. I would appreciate if you could help me with the following set of commands. ...
33 views

### how to delete a variable programmatically in a notebook from another notebook

how to delete a variable programmatically in a notebook from another notebook? c = b; I have already tried Remove[c] but ...
34 views

### Arrange an expression based on variables' names

I have a problem of arranging an expression as shown in the following picture. The first expression exp is derived from other functions and equations. I want to get ...
35 views

### Changing variable order in an output [duplicate]

Is it possible to change variable orders in an output? For example, if i get: x= p l is it possible to change as: x= l p
95 views

### Partial derivatives in a variable name

I would like to create variable with names of the form \[PartialD]g and \[PartialD]\[PartialD]g. Is there any way to do this?
1 vote
73 views

### Full Information Maximum Likelihood - Under some other name in Mathematica

I have recently stumbled upon something called FIML - Full Information Maximum Likelihood. Apparently this methodology helps overcome missing variables provided the gaps are random. Searching the ...
137 views

### What Does this Syntax Mean in Ouput from DSolve?

When I run the code DSolve[y*D[f[x, y, z], z] - z*D[f[x, y, z], y] == 0, f[x, y, z], {x, y, z}] I get the following output. I don't understand this syntax. I ...
70 views

### Integrate of simple equation but is not solving!

I have this simple integral but I don't know why Mathematica can't solve it?! FullSimplify[Integrate[x/(-x^2 + a x + b)^(1/2), {x, Sqrt[b], Sqrt[R^2 + b]},Assumptions -> {a > 0, b > 0}]]
141 views

### Making a list of variables

Consider the following code, which give a Manipulate object that returns the "total" of a certain variable var 1 ...
60 views

### Extracting variables [closed]

Similar to this perhaps, but I prefer a built-in function. I have defined the expression L = a*b*c. Is there a Mathematica function that can identify and extract ...
215 views

### How to replace the arguments of a function?

I have the following type of (very long) expression: $$\ldots + X[1,2,3,5] + X[2,4,5,6] + \ldots \tag{1}$$ where $X[a,b,c,d]$ is some undefined function. I would like to replace all the occurrences of ...