Questions tagged [system-variables]
The system-variables tag has no usage guidance.
73
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Items known by CurrentValue
CurrentValue can be used to poll the state of numerous system values such as the mouse position. Its help page doesn't list all possible items, though. An item like ...
21
votes
2
answers
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Where can I permanently modify $Path?
I've quite forgotten: what file does one modify in order to add directories to $Path globally? Specifically, I want to include ...
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17
votes
3
answers
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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?
- 1,697
17
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1
answer
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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. ...
- 273k
15
votes
1
answer
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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 ...
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12
votes
2
answers
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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 ...
- 61.9k
11
votes
4
answers
327
views
How to change the variables Qi's to Ri's in one or two steps
I was wondering if there is a command in Mathematica to change all the following Qi's to Ri's? For example, change Q1 to R1, Q2 to R2, etc.
...
- 319
10
votes
1
answer
298
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Why do DateList, DateString, and AstronomicalData ignore $TimeZone?
My reading of the documentation for DateList and DateString lead me to believe that both functions use ...
- 12.9k
9
votes
2
answers
981
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, $MachineID can be used but I want to make it safer. Can Mathematica obtain the computer's hard drive ...
- 319
9
votes
2
answers
943
views
How to set the timeout value for *Data functions
I haven't measured this precisely but it seems the default timeout value for retrieving EntityValues with *Data functions is in ...
- 7,827
6
votes
5
answers
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Is there an analogue of the Variables command for general expressions? [duplicate]
The command
Variables[poly]
gives me a list of all variables that appear in the expression poly, which involved sums, ...
- 1,088
6
votes
1
answer
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how to obtain all Messages for Mathematica build-in functions?
Help says Messages[symbol] gives all the messages assigned to a particular symbol. These are called message identifiers per help:
Message names always consist of ...
- 149k
5
votes
2
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Syntax highlighting conflict
I'm trying to syntax highlight this expression: x=$\sqrt{\pi }$//N and from various sources I've learned that x (the assigned symbol) belongs to context Global while the Pi and N belongs to System. So ...
- 5,121
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2
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Equivalent of __FILE__?
Many languages define a special identifier whose value is the path to the source file currently being processed. (For example, in C, this is done through the ...
- 11.7k
5
votes
2
answers
70
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Where is the new System`ConvertersDump`$extensionMappings?
I used to find the extensions mapping from System`ConvertersDump`$extensionMappings, which gives a mapping like "{"*.3ds" -> "3DS"...}&...
- 283
5
votes
1
answer
277
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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 ...
- 9,030
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1
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Setting $RecursionLimit crashes Mathematica 10
I have encountered what I shall presume is a bug: setting $RecursionLimit repeatably crashes the Mathematica 10 kernel:
...
- 273k
5
votes
3
answers
538
views
One inequality with two variables
I would just like to know if this:
((a - b)/(b*Log[b])) - Log[Log[a]] + Log[Log[b]]
exceeds 0 for any combination of a and <...
- 189
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1
answer
364
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How to set UnitSystem permanently
I would like to set the system of units ($UnitSystem) permanently to "Metric".
I know that I can do
...
- 37k
5
votes
3
answers
567
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Creating a variable from Reduce[] output in Mathematica
Say I have the following input:
Reduce[{t*c==50, t==5}]
the output:
t == 5. && c == 10.
Is there a way to create a ...
- 219
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votes
1
answer
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Is it safe to change the value of $TimeZone?
I'd like to configure some of my notebooks to assume all calculations using dates, times and locations (notably AstronomicalData , but others too) take place at the ...
- 12.9k
5
votes
2
answers
506
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 ...
- 12k
4
votes
3
answers
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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?
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2
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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 ...
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votes
1
answer
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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
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votes
1
answer
277
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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
4
votes
1
answer
216
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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 ...
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votes
3
answers
327
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Accessing temporary value of a Nest evaluation
The function Nest[] must store the temporary values in the memory somewhere (those values that would form the entries of the list which is returned by the ...
- 333
3
votes
1
answer
782
views
Solving a large system of nonlinear equations
I have a system of 80 nonlinear equations with 64 variables to solve in Mathematica but it takes a lot of time (about two hours) and then it return "no more memory available" knowing that I have 8GB ...
- 81
3
votes
1
answer
406
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How to restrict global variables to within a given notebook? [duplicate]
Possible Duplicate:
Is there a way to separate variables between multiple notebooks?
I assigned a global variable like a=10; It works in all my notebooks, but ...
- 2,304
3
votes
0
answers
273
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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 ...
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votes
0
answers
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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'...
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3
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Solve the system of equalities and inequalities
I have a system of expressions, in which each expression is an equality or inequality expression of the following form:
Var = Var1 + Var2
Var $\odot$ number
Var $\odot$ Var1
$\odot$ = $\leq | \geq | =...
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1
answer
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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. ...
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1
answer
502
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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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1
answer
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Importing data from excel and assigning a variable to each of its columns
How should I assign variables to the data imported from excel containing 3 columns which are time, mean and standard deviation. I want to perform operations on the three variables to get new variables....
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1
answer
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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
2
votes
1
answer
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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 ...
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0
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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
1
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1
answer
310
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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
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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 ...
- 27k
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1
answer
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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
1
vote
1
answer
1k
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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
1
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1
answer
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How to understand and use DSolve solution
This equation is simple to DSolve in Mathematica, but I don't know how to use and understand solution.
...
- 1,129
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4
answers
311
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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:
...
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1
answer
135
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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:
<...
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1
answer
169
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Plot of phase portrait of system of 4D non linear differential equations
While numerically solving ths system of differential equations:
...
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0
answers
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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 ...
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0
answers
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vote
1
answer
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How do assign an interval of values to a variable in order to use them in a function?
From my code (below) I have K1 and K2 set to zero in order to test this numerical method. However, K1 is on an interval from 0 to 32, and K2 is on an interval from 0 to 8. I would like to know if ...
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