# Questions tagged [system-variables]

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### 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 ...
1 vote
93 views

### Plot of phase portrait of system of 4D non linear differential equations

While numerically solving ths system of differential equations: ...
70 views

### Plot phase portrait of a system of ODE

I have the following system of 4 differential equations: ...
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 ...
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180 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 ...
401 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?
44 views

1 vote
194 views

### 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 ...
93 views

### 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 ...
231 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 ...
5k views

138 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 ...
282 views

### 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. ...
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. ...
205 views

### 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 ...
1 vote
299 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: ...
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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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### 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 ...
887 views

I want to packed my program use RSA algorithm. Of course, $MachineID can be used but I want to make it safer. Can Mathematica obtain the computer's hard drive ... 3 votes 0 answers 262 views ### Shared variables between notebooks using the same kernel not working in mathematica 10.1? I am trying to access the variables over two Mathematica documents, this works fine when I use Mathematica 9 but when I attempt to do the same on 10.1 it doesn't work. I have set both notebooks to ... 5 votes 1 answer 241 views ### Is it safe to change the value of$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 ...