Questions tagged [variable-definitions]
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.
418
questions
1
vote
2answers
86 views
'Do' loop acting on a global variable
I need a code that will allow me to alter a matrix (a global variable) iteratively using a function update (which depends on ...
1
vote
0answers
27 views
Variables with super/sub scripts
So I know how to create variable names with subscripts/superscripts at the end (using ctrl+_ etc), however, how would I use them in the middle of a variable name?
0
votes
0answers
76 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 ...
1
vote
1answer
52 views
Define/store individual elements of Table output for back-substitution
At its core, mine is a very simple communication error between me and Mathematica that I haven't been able to crack, so I do apologise if it seems embarassingly inane.
Please consider the following ...
0
votes
1answer
42 views
Getting error messages form Set while trying to implement the bisection method with a For-loop [duplicate]
My objective is to build a function using modules that runs the bisection method. I have a working bisection method but when I try to implement it as a module I keep getting this error and I can't ...
1
vote
1answer
34 views
Multiple functions compact form
I have a sort of silly question...
I need to define two functions in the following way
...
0
votes
2answers
65 views
Save a Derivative
I have defined the derivative of a function
Derivative[1][f][x_] := Sin[x]
How can I save this definition in a file? Derivatives are not included in ...
2
votes
4answers
114 views
How can we make the input of a function multiple lists?
I want to create a function that takes inputs that are multiple lists of ordered quadruples. For example, when we run the code our input line should read something like inputs[{2,3,4,5},{6,7,8,9},...} ...
0
votes
1answer
45 views
Compact notations for multiple variables
Why does this work
Manipulate[ListPlot[{a[1],a[2],a[3]}], {a[1], 0, 1}, {a[2], 0, 1}, {a[3], 0, 1}]
But this doesn't?
...
0
votes
1answer
42 views
Defined function keeps the variable
I'm a beginner at Mathematica, and I have a problem finding the roots of a function for a specific variable (using Jens' findAllRoots function).
Due to the nature of my problem, I need to compute ...
6
votes
3answers
179 views
KeyExistsQ[] but for functions?
Is there a good way to check if, say, f[5] has been defined if f is a function, similar to ...
6
votes
3answers
411 views
Create variables in a for loop
I am very new to mathematica, but it would be much easier for me to use For loops in order to create variables. My train of thought was simple, but apparantly does not work. Let's say I defined these ...
1
vote
1answer
38 views
Number of values stored in a function
Suppose I run this:
f[0] = 1;
f[n_] := f[n] = 2 f[n - 1];
f[1000]
Now there will be 1001 values stored in f, and ...
2
votes
1answer
37 views
How to Append the value of a variable and not the variable itself
So lets say I have
a = Some complicated code that changes
list = {}
AppendTo[list, a]
Obviously it would give me
...
3
votes
1answer
26 views
Referencing data in sets of sets
Given a data set how to assign definitions to the subsets. For
instance given the data
data = {{0, 1, 1}, {0, 1, 1}, {1, 1, 0}, {0, 1, 1}, {1, 1, 0}}
if {0, 1, 1} ...
14
votes
4answers
771 views
When is a symbol a Symbol? Is there an easy Mathematica way to test if an object is a symbol sort of like a SymbolQ?
Yes I know there is no built-in native function called SymbolQ (but JavaScript does). However, could one be simulated to work for most cases? I often rely on ...
7
votes
1answer
91 views
Is there something wrong with DistributeDefinitions?
I have the following code, which fails to distribute the DownValues for the symbol f. Could anybody please explain what is wrong.
...
0
votes
1answer
65 views
Subscripts use to make expression readable [duplicate]
I am trying to write a function in mathematica which depends on different parameters. For example
$$f(x_1, x_2, x_3, x_4, x_5)= 2x_1+\sin(x_2)+x_3*x_4-x_5^{-1}$$
(My actual function has 12 such ...
2
votes
1answer
155 views
Functions without arguments [duplicate]
In the course of a project recently I had to use a particular function u[x, t] a number of times. Because in mathematics I would typically write this function as $...
2
votes
1answer
62 views
Are symbols automatically generated when defining a variable in the global context and what are symbols?
Abstract: I have noticed something really tricky with Mathematica and the documentation for symbols is short on clearing the confusion. It likely reveals what symbols are but it's not very prominent. ...
10
votes
1answer
233 views
How to clear all definitions matching f[1, …] but not f[2, …]?
I would like to clear all definitions of the form f[1,...] in such a way that f[2,...] remain unaffected.
The two methods I know ...
0
votes
0answers
41 views
Definition of a real variable
I would like to calculate a definite integral with a real parameter "a".
I tried Refine[Element[a, Reals]] and Simbols [Element] Reals but the yield was a ConditionalExpression dealing Im[a] and Re[a]...
0
votes
0answers
32 views
Defining a function with certain regularity (e.g. smooth)
My goal is to understand how Mathematica computes limits that would require differentiability assumptions on functions (for, for instance, L'Hopital or Taylor Series).
Consider, for instance, the ...
1
vote
1answer
47 views
Simplify terms with delayed and immediate function definitions
Say I want to define a function fwith input x but also involving parameter p not yet ...
4
votes
2answers
57 views
Move definition from one context to Global`
Suppose we have the following package ABC.wl.
BeginPackage["ABC`"]
Begin["DEF`"]
f1 = 0;
f2[x_] := x + 1
End[]
EndPackage[]
...
8
votes
1answer
82 views
Local variables in sums and tables - best practices?
Stumbled on Local variables when defining function in Mathematica in math.SE and decided to ask it here. Apologies if it is a duplicate - the only really relevant question with a detailed answer I ...
asked May 4 '20 at 8:00
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2,22710 silver badges20 bronze badges
0
votes
1answer
44 views
SetDelayed using local variables
I'm trying to define MakeBoxes for a bunch of functions all at once, but wish to do so within a loop as in the following example:
...
3
votes
1answer
43 views
New variable in With structure appear as global, and many other strange things I don't understand
I thought I know With and Module until I see this example on Wolfram Documentation.
Below is a demo code:
...
0
votes
0answers
29 views
Evaluating global variable within a module
I'm trying to work with something like the following:
a = b;
f[x_, b_] := Module[{N},
N = Abs[a];
10 N
]
f[1, 1]
The output of running this is:
...
0
votes
0answers
44 views
Set of multivarible expressions to be re-expressed a single variable
I have a set of expression such as $\frac{3x+y-z}{6x}$ and $\frac{3 x-y+z}{12 x}$, which can easily get re-expressed as $p$ and $(1-p)/2$, where $p=\frac{3x+y-z}{6x}$, but is there a way to find this $...
0
votes
0answers
40 views
Problema simulating FindRoot
I am writing a procedure that simulates the findRoot built-in function using the same code that appears at chapter 6 of $\textit{Programming in mathematica}$ by Paul Wellin. The code is the following....
1
vote
1answer
37 views
syntax error when defining a list of matrices: “…cannot be followed by..”
I am literally just defining a list of matrices, but seem to run into the following error when adding the last matrix. (so to be clear, I get no error when I take out the last matrix entry). What's ...
0
votes
1answer
41 views
Assign variable to solve [duplicate]
I would like to assign my result from equation. I tried /. and := but it gives me empty variable. How can i fix it?
1
vote
1answer
35 views
Getting a stored variable from its value
Given a numerical value, is it possible to check whether that value is stored in (or defines) some variable in the notebook?
Maybe if I could list all of the defined variables, then I could simply ...
2
votes
1answer
117 views
Mathematica Won't Recognize a MeshRegion
I've implemented the code in the top answer of this question on the Plateau problem in differential geometry, and it works with the example shown in Example 1, so there is nothing wrong with the code. ...
1
vote
0answers
54 views
How to define an Intermediate Variable [duplicate]
I want to find the relationship between several parameters. But I don't know how to define an Intermediate Variable.
For example:
I want to know the relationship between x and {y,z} which will satisfy ...
0
votes
1answer
29 views
Avoid an Error Message when Importing
Consider the following code
Button["Import", file = SystemDialogInput["FileOpen"];
data = Import[file], Method -> "Queued"]
which yields a button which, ...
0
votes
0answers
12 views
Min of a set defined with conditions
I would like to define this parameter inside a function:
$R = \min\left\lbrace i \in \left\lbrace 1,\cdots,n \right\rbrace \; : \; ((p+i)\mod n) \; \neq a_{j} \; \forall j \in \left\lbrace 1,\cdots,m ...
1
vote
0answers
79 views
Issue with Solve, NSolve, FindRoot
I have this code that I've been trying to get working for some time. I asked some questions before which helped but still struggling!
...
0
votes
1answer
35 views
Issue with variables/functions in solving equations
I've been posting some questions all around issues with defining and using variables/functions in Mathematica.
Based on the answers/comments I got I still cannot make this simple code work... Why is ...
1
vote
1answer
62 views
Table of Variables within Manipulate
Given a certain number n, I want to define n controls within Manipulate with the correct ...
3
votes
1answer
71 views
2
votes
1answer
77 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
3answers
91 views
Is it possible to use a previously defined value in subsequent definitions of a `Block`?
Is it possible to use a previously defined value in subsequent definitions of a Block?
According to syntax coloration, this should work as expected, that is, ...
0
votes
0answers
50 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 ...
4
votes
1answer
78 views
Defining list of new variables at once (in a loop?)
I have a list of solutions Subscript[x, 1][t], i = 1,...,n (n given).
I would like to use these variables to define new variables such as:
...
2
votes
2answers
52 views
3
votes
1answer
73 views
How to access all instances of a defined function
This should have a simple solution, but for some reason I cannot find how to do this.
Let's say I have a "function" where I have defined values (in my actual example I have many instances of this, ...
0
votes
0answers
37 views
Series expansion of explicit functions
For the following input,
zv[u_, v_] := v + zv1[ u, v]/u;
mvu[u, v] := D[zv[u, v], u];
Series[mvu[u, v], {u, 0, 1}]
the output is
...
1
vote
1answer
96 views
Basic Question: how should I read this instruction?
I'm very new at using Mathematica and it's not my Job. It's just something I like.
...
