# 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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### Module inside With, With inside Module, or Just Module?

In general, if one wants to define local variables and local constants, which of the following is the best programming practice in terms of performance and code "safety"? (Assume ...
66 views

### Variable assignment/replacement issues

I have three questions about variable assignment. Module[{z}, z = y; p'[y] /. p -> Function[y, Evaluate[z]]] When I run the above code, it outputs 0. 1) If I ...
75 views

### Define variables dynamically to compute a function

Let's say I have defined a function $W(p, q)$, where $p$ and $q$ are integers between (and including) $0$ and $2$ and the function takes me to a real number. Upon an input $n$, where $n$ is a positive ...
107 views

### Why some variables get substituted and others don't

I was running into some trouble with my math and I whittled it down to this nugget: ...
57 views

### Issue with calling one notebook from inside another one

I am calling one notebook (N2) from inside another notebook (N1). The results are transferred correctly from the second notebook to the first one. But when I try to compare the results from the two ...
610 views

### How to declare variables with plus/minus sign as subscript/superscript?

I am pretty new to mathematica, so please forgive me if I ask any stupid questions. I want to create a vector $a^{+}=[a^+_{k-2},a^+_{k-1},a^+_{k},a^+_{k+1},a^+_{k+2}]$ and then do some symbolic ...
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 ...
1 vote
30 views

### Error using list of discrete variables with WhenEvent

I came across an error when using a list of Discrete Variables with NDSolve and WhenEvent. As you can see in the minimal example, where I defined the 'testevent', when I use ...
1 vote
32 views

### How to change expression of variable in output

I run the example： c = a - b; e^(a - b) This gives me e^(a-b). How can I do to let it output e^c
1 vote
51 views

### How to return a variable name and value from within a self-contained function block?

Abstract: I have viewed other solutions on StackExchange but none actually address using a fully self-contained function to return name and value of a variable. The only function that works requires ...
1 vote
42 views

### Problem in importing function in NDSolveValue

I have a code for solving a system of 2 differential equations (sol1). Given that what's inside is a bit heavy, I define functions so that I can call them. My issue is that when I write everything ...
1 vote
87 views

### Execute a notebook with a changing variable

I have created a notebook with one fix variable that I want to run from 1 to 100. Every time the whole notebook (all cells) shall be executed for the given number. At the end of the notebook, it shall ...
1 vote
52 views

### How to avoid import evaluation until if wil return true

My goal is to import a data from url that depends of 1 parameter, this initialy value is null or undifined en yo have to selec some popup and then the variable has value, what is the method to do that?...
1 vote
76 views

### Settings to disable global scope

I am building a fairly large application in Mathematica, and globally scoped variables are causing issues. I would like globally scoped variables to be out-of-scope for my expressions, except by ...
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 ...
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 ...
100 views

### Creating new variable names, Symbol or ToExpression

One can create new variable names by Symbol : In Table[Symbol["x"<>ToString[i]], {i,1,5}] Out {x1,x2,x3,x4,x5} But it is also possible to ...
63 views

### A function that maps Held symbol to string

Rougly my question is about constructing a function that maps Hold[var] to "var" even when var has an assigned value. In details : ...
33 views

### Minimizing a function and plot it

I have a long expression, depended on 3 different variables say "a", "b" and "p". Just as an example, a part of this expression is: z = p * Cos[x] * Sin[y]. I'm going to ...
42 views

### Assign Variable to NSolve

I'm looking to create an interactive region plot in Mathematica, and it's quite a complicated region (seen below).. The variable p is actually a function of y, and it's too hard to solve analytically. ...
44 views

### Replace the output of a module containing local variables by their actual value

I want to construct a function as the output of a Module, but I obtain the local variables as part of the output. This is a problem when I try to construct many of these functions in a parallel table, ...
79 views

### Issue with several replacements in a function under certain conditions

I am trying to define a function (reduce[x]) which does several substitutions, depending on the values of certain parameters. Concretely, consider an expression x, which contains an arbitrary number ...
164 views

### Using an if statement to assign a value to a variable

New Mathematica user here. I'm using some code from a colleague and editing it to give me more specific results in finding the zeros of a complex polynomial. I am attempting to find a way to assign a ...
56 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 ...
64 views

### ReplaceAll Not Working Correctly

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

### assigning numerical values to variable

I have a csv data file, has two columns of data. First column denotes time (t) and the corresponding value in the second column is flow rate (f). I would like to assign these values to an array f[t], ...
347 views

### What are the valid symbol names for packages?

Regarding to the message: ...
88 views

### The conditions used in Sum or ParallelSum: Calling a function/variable

For some reason, I encounter a problem when doing the Sum and ParallelSum (or doing the Do or ParallelDo, e.g. such as the issue here), I figured that the potential cause of the problem can be ...
72 views

### to reduce the unknowns of a set of equations with several symbolic coefficients, e.g. using the GroebnerBasis

I have a set of $4$ equations with $4$ unknowns $\theta_1$ to $\theta_4$, and would like to eliminate the number of unknowns, to get a smaller set of equations, e.g. $n$ equations with $n$ unknowns, ...
639 views

### Extract fit error from parameter table to use as a variable

Is there anyway to extract the fit error and store it in a variable. I have done something similar to use actual fit results as ...
47 views

### Similar Variable Names

I have variables $X1,...,X10$ and $X1hat,..., X10hat$ in a system of equations. How can I refer to these variables in a summation? I am looking for something like: ...
478 views

### Colors of variable mathematica

Suppose that I have an equation which goes like this: x = 2; yp = 2; y_p= 2; a = x + yp + y_p; Usually, once the variable is defined it will be of blue color and ...
75 views

### Using sub-scripted variables in functions

Is it possible to use subscripts in Mathematica functions, for example f[Subscript[x, a] _] := x^2 However this doesn't seem to work, is there a way to allow ...
92 views

### Best practice for passing variables to many functions?

I am rewriting an application in Mathematica. The previous version used global variables, which I find distasteful, but to avoid it I am needing to pass several static Datasets and Associations around ...
What is the best way to a create a symbolic variable to represent Class Conditional Probability in Mathematica e.g. $p(A|B)$