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.
502
questions
7
votes
4
answers
276
views
Create a list of indexed variables and assign values in one line of code
It is easy to create a list of indexed variables
F/@{1,3,6,8}
I would like to assign values in the same line of code
...
- 183
1
vote
1
answer
83
views
How to save a definition in one file and update it easily?
When running a task which needs a long time for computation but returns a simple result, I often do this:
...
- 51
1
vote
0
answers
35
views
Sending definitions from the subkernels to the kernel
Sometimes it is convenient to define an indexed quantity g[i] as in
f[i_] := (Pause[5]; i^2);
Do[g[i] = f[i], {i, 10}];
A ...
- 651
0
votes
1
answer
44
views
How to define the following rule for all objects in a compact way?
Consider the following symbolic definitions:
...
- 4,642
0
votes
1
answer
67
views
Interpolation error to generate a two variable function
I am facing some issues with performing an interpolation. From the image, you can find the values in three columns, the 1st column is x, the second column is ...
1
vote
2
answers
80
views
Changing part of a list of unequal arrays
I have {x, y, f(x,y)} data in multiple (n x 3) arrays with unequal length, which I read in from different files in order to later plot them using ListPlot3D. I ...
- 13
0
votes
0
answers
45
views
how to use subscripted variable such as a_i as the control of Manipulate?
I'd like to define a series of variables called $l_1$,$l_2$, etc., in Mathematica, using the "ctrl+_" shortcut. Moreover, I want to use these variables as the controls of a Manipulate[] ...
- 695
0
votes
0
answers
19
views
Specifying and assigning arguments of a function to be real
I have the following complex matrix that I wish to integrate (element-by-element)
...
- 375
2
votes
1
answer
71
views
How to directly define a function as the solution of RSolve
This is probably very simple, but I just cannot find this anywhere online. I have the code
...
- 35
1
vote
1
answer
51
views
Function definition inside Module with local symbol
Usually if I want to define a function using an expression I do:
expr=x^2;
f[x_]=expr;
which usually works and give f a defination.
But now if I want to do the ...
- 151
0
votes
1
answer
35
views
What is the relationship between a list of symbols created by a specific name, and a expression with such a name?
I'm trying to create a list of symbols called "x" for calculating symbolic gradients of some functions, so I write:
...
- 3
1
vote
1
answer
90
views
Doing algebra with differential operators
I'm doing some work on stochastic processes, where I use random functions which are defined by their properties over averages, i.e $$\langle f(t) \rangle =0 \\ \langle f(t) f(t')\rangle = \alpha(x,y) ...
- 11
2
votes
0
answers
69
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
80
views
checking if a variable is defined
How can I check if a variable is defined?
Definition[foo]
produces: Null, but:
...
- 1,141
2
votes
5
answers
274
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:
...
- 162
2
votes
1
answer
83
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
...
- 4,047
1
vote
1
answer
80
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::...
- 117
0
votes
0
answers
70
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
135
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 ...
- 1,258
0
votes
1
answer
82
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
218
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 ...
- 1,516
1
vote
1
answer
118
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
68
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 ...
- 133
2
votes
1
answer
108
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). ...
- 143
0
votes
0
answers
44
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
36
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
473
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 ...
- 369
1
vote
1
answer
79
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
47
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 ...
- 111
0
votes
0
answers
73
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:
...
- 139
2
votes
1
answer
169
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
86
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
162
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
169
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 ...
- 207
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 ...
- 427
2
votes
1
answer
102
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
116
views
6
votes
1
answer
342
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,
...
- 2,079
0
votes
1
answer
82
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
...
- 2,688
0
votes
0
answers
147
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 $v$ ...
- 592
0
votes
0
answers
109
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?...
- 4,047
0
votes
1
answer
197
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< ...
- 55
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
257
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 ...
- 215
8
votes
0
answers
171
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
64
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
94
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
113
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 ...
- 115
1
vote
1
answer
170
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
86
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