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.
492
questions
2
votes
0
answers
54
views
Argument value loss using Listable C-Compiled Function
In my recent studies, I have come across a very strange anomaly with C compiled functions. When I call a function that has the 'Listable' attribute while global variables are accessed through ...
1
vote
0
answers
38
views
checking if a variable is defined
How can I check if a variable is defined?
Definition[foo]
produces: Null, but:
...
- 1,131
2
votes
5
answers
237
views
Repeating definitons of variables
I have the piece of definitions
y = 1;
x = 2;
n = 2;
a := (y^(x - 1) + n)/(y^(x - 1) + y^(x - 2))
I want to keep defining y as a by doing:
...
- 139
2
votes
1
answer
81
views
Defining function for decimal value k[0.5+0.5]
k[1 + 1] = 2;
k[1 + 0.5] = 1.5;
k[0.5 + 0.5] = 1;
{k[2], k[1.5], k[1]} // TableForm
2
1.5
k[1]
Can you explain this phenomenon? I think the output should be
...
- 3,561
1
vote
1
answer
68
views
How to avoid using the principal branch?
How can I make Mathematica to use $Log[-1]=i\pi+2i\pi*n$ with $n\in\mathbb{Z}$?
Currently, mathematica set $Log(-1)=i\pi$ and when I try to redefine the value of $Log[-1]$ I get the message "Set::...
- 121
0
votes
0
answers
67
views
Can you dynamically create variable names in Mathematica? [duplicate]
I was wondering if there is a way of Mathematica to read a string or number and create variable with that name.
For instance imagine that I have a file with the word data1. I would want to create a ...
2
votes
2
answers
106
views
The way of converting a string to a variable in a loop?
I have 60 txt files which I want to import them into Mathematica using a Do loop. Each file contains some numbers (more precisely, a list of numbers). I want to put ...
- 1,228
0
votes
1
answer
81
views
Global order setting
I'm working on mathematical models using many alphabets and Greek characters as parameters or variables. However, The outputs show them in undesired order. Here are some examples:
...
- 1
2
votes
2
answers
211
views
How to implement Newton's Identities
I need to produce identities related to Newton's Identities of arbitrary order. More specifically, I need the identities in the following image for an arbitrary n:
What I can't quite wrap my head ...
- 1,496
1
vote
1
answer
86
views
My ParallelDo does not work
I have to do a lot of calculations that take lot of time, and using a Do loop is simply too long. It is the first time I am using ...
- 33
1
vote
1
answer
60
views
Initializing a system of abstract functions with a for loop [closed]
I am trying to initialize a collection of abstract functions $\theta_k(t)$ in a variable $t$ where $1\leq k\leq n$.
I cannot define them explicitely; the entire point is that I want to numerically ...
- 111
2
votes
1
answer
99
views
SystemModelLinearize
The following are the state matrices A and B obtained by linearization using SystemModelLinearize ("DocumentationExamples. Modeling. Generator" is the circuit given by the official routine). ...
- 53
0
votes
0
answers
42
views
Strange behavior with setting multiple values simultaneously
I'm having some strange behavior when trying to set multiple variables using {x,y,z} = {1,2,3}.
When I enter "{a,b,c,a',b',c'} = {1,2,3,4,5,6}", it sets a,b,c,a',b',c' to 1,2,3,4,5,6 as ...
- 101
0
votes
0
answers
24
views
Changing list of variables in text file
Imagine I have a .txt file as follows
var1 = 2;
rate = 10.3;
power = -12;
I want to use Mathematica to automatically update these values and rewrite the .txt file ...
- 4,362
0
votes
0
answers
27
views
save function only for particular arguments to file
Define
f[2] = 3
f[3] = 5
I know how to save the function to file: ...
- 1
2
votes
2
answers
432
views
How can I make 10 variables from a for loop?
I used a for loop to make 4 variables:
For[i = 0, i < 4, i++,bi=0]
But when I write b0 or ...
- 359
1
vote
1
answer
76
views
How to define functions using $Z_2$ coefficients and $Z_N$ variables, e.g, realizing $1+1=0$?
A minimal example is to realize the following:
$x+x = (1+1)x = 0$, and $x^{N+1}y^{N+1}=xy$,
where $N$ is a given positive integer.
- 113
0
votes
0
answers
41
views
Reusing local variables through Reduce and ToRules
Problem: I am interested in solving a system of linear equations through Mathematica. In my current test scenario, I am having trouble using the Reduce function followed by the ToRules command. I ...
- 101
0
votes
0
answers
44
views
Getting .wl file without appending global' before variable names
I have a .wl file created using mathematica that contains:
list = {{a->4, b->5}}
When I read it in using Get["file.wl"] it reads in as:
...
- 55
2
votes
1
answer
121
views
Can you use superscripts as variable and function names?
I want to express the following function:
$z^{(1)}=w^{(1)}a^{(0)}+b^{(1)}$
I have read in Mathematica documentation that Symbolize can be used to define variables ...
- 323
1
vote
0
answers
70
views
Why =. is not clearing the value of a variable in this case? [closed]
I am reading "Mathematics and Algorithms" as part of the Wolfram Tutorial series.
In "Values for symbols" section of the "Algebraic Calculations" chapter it is described ...
- 323
6
votes
3
answers
148
views
How to define variables $a$,$b$,$c$,$d$ are all elements of set $\{2,3,5,7\}$?
I would appreciate it if somebody could help me with the following problem:
I want to create a Wolfram Language expression that states that all $a$,$b$,$c$,$d$ variables are elements of the set $\{2,...
- 259
5
votes
3
answers
160
views
Get the symbol name of the function's nth argument
I tried this:
Plo[fun__] := SymbolName @ Part[List @@@ Unevaluated @@ {Hold[fun]}, {1}, 2]
SetAttributes[Plo, HoldAll]
On ...
- 185
0
votes
0
answers
67
views
How to define variables properly in mathematica, a variable with two name [duplicate]
I wanted to define a variable in the name "beam_frequency", this is quite possible in other programming languages like python and Matlab. How to define two pair variable name in Mathematica ...
- 417
2
votes
1
answer
87
views
Implement recursion one step at a time with a function of more than one variable
i am trying to implement a recursive difference equation step by step, by implementing rules, similar to Rojo's method in this thread: How can I evaluate only a single step of a recursive function?
...
- 23
8
votes
1
answer
114
views
0
votes
0
answers
40
views
How can I "map thread" similar notation definitions in one line?
In the past few days I have been dealing with different integral notation definitions made by myself. I have noticed several similar notation definitions with a common pattern, but currently I am only ...
- 453
6
votes
1
answer
272
views
Is K is a function? [duplicate]
Some of the capitalized single letters are functions. Starting a fresh kernel and typing in the 24 capital letters, the following letters turn black since they are special functions,
...
- 2,049
0
votes
1
answer
76
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
...
- 2,822
0
votes
0
answers
73
views
Global assumption non zero
I would like to define globally an assumption stating that I have a nonzero real vector $v$.
For now, I put :
$Assumptions = Element[v,Vectors[{100},Reals]]
but $v$ ...
- 496
0
votes
0
answers
108
views
See variable as byte
I see variable v is occupying 112 bytes of my RAM.
v = {3, 5, 7}; ByteCount[v]
112
Then how to see the content of the 112 bytes?...
- 3,561
0
votes
1
answer
130
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< ...
- 35
0
votes
0
answers
36
views
How can I prevent functions and variables from being automatically cleared when I close Mathematica? [duplicate]
The following happens with every notebook I make:
I define functions and variables.
When I quit Mathematica and reopen the notebook, all of those definitions have been cleared. The functions and ...
- 1
2
votes
2
answers
201
views
Why is the parametric plot failing?
I tried running the following code but it doesnt seem to be working, it seems to be stuck on running. I think it's got something to do with the way I am defining functions with a variable integration ...
- 155
8
votes
0
answers
135
views
Defining a SparseArray functions in Mathematica 13
I am defining a sparse array as a function of argument x, i.e.
f[x_] = SparseArray[{1->x}, {3}]
In Mathematica 12 this works perfectly, I can pass arguments and ...
- 81
0
votes
1
answer
59
views
Part of array as a blank variable [duplicate]
I have a little question.
Let me define the function:
f[k_]:=k
So 'k' in the argument of 'f' is a blank variable.
Is there a way to define a part of array as a ...
0
votes
1
answer
85
views
Errors appear after integration of an interpolating function
I have a little question about integration of an interpolating function.
There is an error in assumptions of the integral.
I have a function that was obtained with an interpolation method:
...
1
vote
0
answers
101
views
Plot implicit function with intermediate variable
Cross-posted in Wolfram Community.
Here, I intend to plot a 3D picture of
with two implicit functions
where $x, y, t, \xi, \eta$, are variables. Of course, these variables can be constrained to ...
- 103
1
vote
1
answer
112
views
Numerical integration in one variable, of a multivariable interpolation function
I create the following set of data:
newmatrix = Flatten[Table[{t, v, new[t, v]}, {t, 0, 2 Pi, Pi/4}, {v, 0, 1,
0.01}], 1]
where
...
1
vote
1
answer
82
views
expression evaluation for Compile[] too time consuming
I need to use Compile[] for a very large expression to be integrated. But for Compile[] the expression has to be evaluated, and this takes endless time.
The expression is composed of several functions ...
- 135
2
votes
2
answers
90
views
Problems with TagSet
I am new with TagSet and TagSetDelayed and I'm not understanding properly how they works. I introduced the following definition:
...
- 141
0
votes
1
answer
51
views
Is always possible to define a numerical value using subscript?
In this code I defined some values using subscripts and it is not the first time I did this but strangely the code execution crashes. To follow the code.
...
3
votes
2
answers
175
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
...
- 4,362
1
vote
2
answers
78
views
Remembering function definitions across sessions to avoid recalculation [duplicate]
I'm working with some large expressions and fourier transforms, which usually take a long time to compute. When I save my notebook with outputs to all my inputs, I'd like it to remember those ...
1
vote
0
answers
46
views
Defining a function expression [duplicate]
I'm sure this has been answered before, but imagine I have the following function
...
- 4,362
0
votes
0
answers
47
views
Matching two lists and create variables
I have two lists of the same length. One of the lists has all the variable-names in it and the other one is a list of lists in which each list represents a value.
I now want to automatically create as ...
2
votes
2
answers
99
views
Unexpected Behavior in `Sum[a + Subscript[a, 1], {a, 1, 2}]`
The simple command
Sum[a + Subscript[a, 1], {a, 1, 2}]
gives the unexpected result
4 + Subscript[2, 1]
while what I want is $3+...
- 1,009
7
votes
2
answers
276
views
Copy a function instead of referencing [duplicate]
Is there an option to let me assign the old function of f to g, without changing g when reassigning f?
This piece of code describes my problem:
...
- 563
3
votes
1
answer
86
views
Performing matrix tensor product and getting a sum of its negative entries
I am given a $3 \times 3$ matrix $M$, which only has real entries.
Is there an efficient way to do the following two operations with $M$?
For a given input $n$, compute the $n$-fold tensor product $M^...
- 175
2
votes
1
answer
96
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 ...
- 175