Questions tagged [system-variables]
The system-variables tag has no usage guidance.
70
questions
5
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2
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Where is the new System`ConvertersDump`$extensionMappings?
I used to find the extensions mapping from System`ConvertersDump`$extensionMappings, which gives a mapping like "{"*.3ds" -> "3DS"...}&...
- 273
0
votes
0
answers
46
views
Identifying the parameter that flips the solution
I have solved a system of ODEs numerically. As the plot shows, the solution SolJx is positive for the parameters I have chosen. However, if you decrease (more ...
- 407
1
vote
1
answer
103
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Plot of phase portrait of system of 4D non linear differential equations
While numerically solving ths system of differential equations:
...
- 51
0
votes
1
answer
72
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Plot phase portrait of a system of ODE
I have the following system of 4 differential equations:
...
- 51
0
votes
0
answers
21
views
Replacing System` definitions in a context whilst still maintaing acces to them [duplicate]
Given the system operator TensorContract I can define a new one, TensorContractLazy with the attribute ...
- 872
2
votes
1
answer
96
views
Composition of functions not working [closed]
I am trying to set a function within a function. What I do is to first create a function with two arguments. Then I would like to set a new function with the same two arguments, in which the previous ...
- 125
0
votes
0
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63
views
How is it possible that $SystemMemory is set to zero?
For one of my Windows machines (Mathematica 12.x.x, only one of them) apparently $SystemMemory returns 0 (zero). I'm unable to do anything with that, since ...
1
vote
1
answer
115
views
How to obtain numerical solutions of a system of two equations with two unknowns?
I have two equations with two unknowns $-10<x<0$ and $0<y<15$
$$3 y \cosh (4 x) \cos (y)+(2 x+5) \cosh (x) \sin (y)=0,\\3 x \cosh (x) \cos (y)-(2 x+5) \sinh (x) \cos (y)=0$$
I would like ...
user80187
4
votes
1
answer
207
views
Square root problem
Consider the following code
NDSolveValue[{
x'[t] == x[t]^a,
x[0] == 0
}, x, {t, 0, 10}]
which solves the equation $x'(t)=x(t)^a$, for some exponent $a$, with ...
- 4,167
1
vote
1
answer
104
views
Programmatically defining variables
I seems as though what I am interested in is unconventional, but I am interested in defining a number of different variables programmatically.
For example I can write a matrix of variables by doing:
<...
- 860
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0
answers
68
views
0
votes
0
answers
37
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Is there a way to automatically store the output of a command to a variable directly?
Generally I do a computation then I have to manually take that number and make it equal to another variable which I define which I can then use to do subsequent computations. Something like this:
<...
1
vote
1
answer
260
views
How to build a tri-diagonal matrix [closed]
I have an algorithm that works for a Tri-Diagonal matrix in Mathematica, but I need a good way to build my starter matrix A. It's a 20 variable system (and will be a 200 variable system once I get it)...
- 25
1
vote
1
answer
1k
views
How to obtain non-trivial solution?
I have the following system of equations.
$ quad\quad\quad\quad u+\alpha v+v+e^{\frac{i \alpha }{2}} (\alpha -1) x=\alpha u+e^{-\frac{1}{2} (i \alpha )} (\alpha +1) z, +u+v=\alpha (v+w)+w+y, (\...
user70481
6
votes
1
answer
193
views
how to obtain all Messages for Mathematica build-in functions?
Help says Messages[symbol] gives all the messages assigned to a particular symbol. These are called message identifiers per help:
Message names always consist of ...
- 137k
0
votes
0
answers
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 $...
- 1
4
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3
answers
417
views
variable K cannot be deleted
If a value is assigned to a variable that is named by capital K it cannot be deleted. This effect can be observed directly after start of the program.
Is this a bug?
- 563
2
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0
answers
52
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What is the purpose of the two variables Global`args and Global`dims [duplicate]
When opening the mma, I find that two variables Global`args and Global`dims have been defined. One can check them by running <...
- 21
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40
views
Differential equations system's solutions differ when one of the constant is 0
I am solving the following system of equations with Mathematica.
$u'=-k_{1}ux+k_{2}x^2, x'=k_{1}ux-k_{2}x^2$
and I obtain the solution for x:
$x(t)=\frac{e^{k_{1}C_{1}(t+C_{2})}k_{1}C_{1}}{-1+e^{k_{1}...
1
vote
0
answers
201
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NDSolve 2 functions 2 variables with intermediate calculation : (1 time-space eq) + (1 space eq)
I have a system of differential equation with this structure :
$$\left\{\begin{split}&\partial_t n(t,r) + \nabla. \big(n(t,r)v(t,r)\big)=0 \\ & f\Big(n(t,r),v(t,r),\partial_r n(t,r),\partial_r ...
- 1,245
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1
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94
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How to put equations in Block or Module to return n values?
i have this code it return EigenValues, it's all right.
Problem:
i have to specify n in order for summation and solution to give output.
Solution:
i just need ...
user63891
5
votes
1
answer
246
views
How to reset a built-in symbol to its default definition?
I'm trying to add functionality to some of Mathematica's built-in functions in a package I'm building. I'm not trying to overwrite any functionality—just add it where it isn't already defined.
I ...
- 8,950
0
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0
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143
views
Minimize and Table of variables
I use a list of variables to Minimize a particular quantity
{ Q, val1, Table[Pi, {i, 1, m, 1}}
where i is the subscript of P. However in this way I have
...
- 1
2
votes
1
answer
285
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Solving equation with multi variable matrix input
Background, here are the equations that I am trying to solve:
Where R, E1, E2, V1, V2, P are all user inputs. X/A goes from -2 to 2 and Z/A goes from 0 to -2. Below is the code that I have so far. ...
- 41
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votes
1
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69
views
Choice of variables name affects the behavior of expression evaluation
I tried to expand this polynomials. With x, it is increasing with the right order, however with b it is in a random order. The only difference is that I change b to x and it works.
...
- 11
12
votes
2
answers
619
views
Catching MachineUnderflow in Version 11.3
Ilian's answer to question 72229, involves
SetSystemOptions["CatchMachineUnderflow" -> False]
Evidently, this worked in earlier versions of Mathematica, but ...
- 60.7k
0
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1
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519
views
How to permanently modify the $Path in Mathematica [duplicate]
I was trying to add permanently a path inside $Path.
"/Users/Softwares/HEP_Softwares/MT-1.0"
Following $Path manual I did the following
...
- 1,604
1
vote
4
answers
308
views
Solving a system of equations for a fraction
I want to solve a system of equations not for one specific variable but for a fraction of two variables. How can I do that?
I want to solve:
...
- 15
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votes
0
answers
263
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How can I globally change $Path permanently? [duplicate]
I have two packages that I would like to append to $Path. I have looked at this link for help but after I quit Mathematica, I have to repeat the process again.
Where can I permanently modify $Path?
...
- 1
0
votes
2
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100
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Sum elemets of an array
I am not sure this is something that is possible to implement in mathematica, but my question is the following.
I have a system three linear equation where the coefficients in front of each variable ...
- 87
5
votes
2
answers
385
views
Where does Mathematica get the value of Environment["PATH"] on newer version of OS X?
Under macOS Sierra, at least, where does Mathematica (currently 11.2) get the value of Environment["PATH"]?
A comment to the accepted answer at Why does ...
- 11.8k
-9
votes
1
answer
167
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How can I find the collision time of 2 ellipsoids that rotate with infinite speed? [closed]
I have 2 ellipsoids:
...
- 35
4
votes
2
answers
1k
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Solve says my system of equations has no solution
I got a system like this (just for example):
I need to get some of the variables expressed in a form like the following.
x == (z - z1) Tan[α1q - μ ] + x1
Let's ...
- 87
4
votes
1
answer
172
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Complete list of values for \$SystemID, \$OperatingSystem
The documentation lists some "typical values", but it leaves out some; e.g. "Windows-x86-64". Also, if the main difference between the two variables is that ...
user45739
1
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0
answers
102
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5
votes
3
answers
506
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One inequality with two variables
I would just like to know if this:
((a - b)/(b*Log[b])) - Log[Log[a]] + Log[Log[b]]
exceeds 0 for any combination of a and <...
- 189
0
votes
1
answer
532
views
Why is N not valid as variable in ParametricPlot? [closed]
Why is
ParametricPlot[{Log[N!], Log[Sqrt[2 Pi N] E^-N N^N]}, {N, 1, 10}]
not working when
...
17
votes
1
answer
351
views
Can one effectively edit a Front End Resource that is already loaded?
A number of special definitions are loaded from .tr files on Front End initialization and are accessible via FrontEndResource. ...
- 270k
1
vote
1
answer
129
views
How to make the variables in $init.m$ not impact the autocompletion
The autocompletion is very convient in Mathematica,but it will make one annoying sometimes when you have a ton variables.I give a scene I encounter.I usually make ...
- 26.3k
4
votes
1
answer
354
views
How to set UnitSystem permanently
I would like to set the system of units ($UnitSystem) permanently to "Metric".
I know that I can do
...
- 36.2k
15
votes
1
answer
412
views
Interpretation of the result of ?@
This might be a very trivial question but as a beginner, I don't know the answer. I was exploring ? and after running a cell containing ...
- 1,584
2
votes
1
answer
69
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Newbie Issues with Solving & Plotting a System of equations
I'm having some problems with my mathematica code, I think I'm overlooking something simple. I get valid solutions for u0 thru u4, but it doesnt generate any plot at all. Also, I'd really like to plot ...
- 23
9
votes
2
answers
916
views
How to obtain the computer's hard drive serial number, BIOS ID, CPU number, MAC and so on use Mathematica?
I want to packed my program use RSA algorithm. Of course, $MachineID can be used but I want to make it safer. Can Mathematica obtain the computer's hard drive ...
- 319
3
votes
0
answers
262
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Shared variables between notebooks using the same kernel not working in mathematica 10.1?
I am trying to access the variables over two Mathematica documents, this works fine when I use Mathematica 9 but when I attempt to do the same on 10.1 it doesn't work.
I have set both notebooks to ...
- 31
9
votes
2
answers
899
views
How to set the timeout value for *Data functions
I haven't measured this precisely but it seems the default timeout value for retrieving EntityValues with *Data functions is in ...
- 7,797
15
votes
2
answers
667
views
How to programmatically ask if Mathematica is running as an Administrator
To avoid execution problems in a program I need to know if Mathematica has been "Run as administrator". What would be the cleanest way to programmatically getting this information?
- 1,657
3
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0
answers
91
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Where can I find detailed information about the SystemOptions?
I'm looking to optimize my Mathematica script, and I'm willing to go spelunking with low-level system options.
The problem is that I've been looking in the Mathematica documentation, but there doesn'...
- 417
4
votes
1
answer
252
views
Mathematica not seeing my environment/system variables
I'm trying to access my environment variables in Mathematica, but I get a Failed result every time. For example:
$ echo $USER
jlconlin
but in Mathematica I do:
...
- 247
-7
votes
2
answers
259
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Module function corrupts string? [closed]
I have the module who should replace some elements of a matrix with checkboxes
...
- 363
2
votes
1
answer
499
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strictly positive solution to $Ax=b$
How to find in mathematica one real strictly positive solution, if any, of $Ax=b$. A is rectangular matrix.
Thanks
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