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Questions tagged [differential-equations]

An equation that relates some unknown function itself and its derivatives of various orders.

An equation that relates some unknown function itself and its derivatives of various orders, for instance x'' = g (free fall) or x' = v (movement under constant speed). Developers solve differential equations numerically or write symbolic engines to solve analytically.

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I would like to solve a system of network-based differential equations using python 3.6

I would like to solve a system of network-based differential equations using python 3.6. The system of equations is as follows: dx_i/dt = omega_i - epsilon_i * y_i * x_i - mu_i * x_i, dy_i/dt = epsilon_i * y_i * x_i - zeta_i * y_i - rho_i * y_i…
BLESSINGS MUFOYA
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Problems solving 3 equations dependency variables in c++

The equations are here Hi! I tried to solve 3 pde equations by using the FD method in C++, but I do not know why I got half of the exact answer at all time. These equations are dependency variable. I have problem with g(x,y) and g(y,x). When I…
john
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How to make a quiver plot for a differential equation using matlab?

y=3-2y is my equation. I have been studying matlab and I cannot understand how to make a quiver plot for this differential equation. I wanted to know how it behaves as it reaches infinity, graphically using matlab.
Ali Haider Soni
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Python: ValueError: setting an array element with a sequence. Error while solving simple ode

I have written a simple python code to simulate adaptive fuzzy sliding mode control. My problem is no matter what I do, I get this error. I tried converting list to arrays etc. But to no effect. Kindly help me iron out this issue. What I am trying…
Amardeep Mishra
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Inizialize a complex array

I'm trying to solve a system of complex differential equation. I would like to fill the complex vector xi[n] with a gaussian valued function. But, when I check the output file, it gives me just a lot of zeros. I gave the input values using the cin…
Gbp
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ode45 system second order

i have write this program but it's not working function xprime = exh(t,z) xprime = [z(2); 30*z(3) - 40*z(1); z(4); 30*z(1)+30*z(5)-60*z(3); z(6); 30*z(3)-40*z(5)]; tspan=[0,200]; Z0=[0.05 0.04…
Kind Fatamii
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Solving fractional differential equations in Matlab using fde12 function

function dfdt=myfun(t,x) dfdt = [... x(2); (1.5*((x(2))^2)*(cos(3*(x(1)))))-(((pi/2)^2) * ... (sin((pi*t)/2)))-(20*((x(1))-(sin((pi*t)/2)))) - ... ((0.5*((x(2))^2)*abs(cos(3*(x(1)))))+0.1) * ... …
Milad Greeneyes
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C++ code running slow after a few seconds

I have C++ code which solves a partial differential equation numerically. Everything works fine, but after the first 10 or so iterations, the code starts to run about 3 times as slow. Some possibly relevant information: I am using the package Eigen…
user1968603
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Sympy second order differential equation

I'm trying to solve free fall equation and i dont understand what's the meaning of the error.
Seward Hercules
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RK4 Python Explanation

I'd like to use an implementation of RK4 I found online for something, but I'm having a bit of difficulty wrapping my head around the implementations I have found online. For example: def rk4(f, x0, y0, x1, n): vx = [0] * (n + 1) vy = [0] *…
aeiou
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How to solve this differential equation in Python?

y''' + yy" + (1 - y'^2)= 0 y(0)=0, y'(0)=0, y'(+∞)=1 (The +∞ can be replaced with 4). The above is a Falkner-Skan equation. I want to get the numerical solution from 0 to 4. Actually, I have read the book Numerical Methods in Engineering with…
Smithermin
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Is there any Tool for analyzing the Influence of variable

When you write a program with lots of code, its difficult to find out which values have a big influence of your final result. In my case i have got a few differential equations which I solve with odeint. It would take a lot of time to find out which…
qwertz
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Implicit Euler for stiff equation

Problem: solve stiff different equation Method: implicit Euler Plan: I calculate next 'y' by solvin non-linear equation use secant mehod. My function is dy/dx = sin(x+y) There is right solution . I used newton…
Tiel Wir
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How can I solve this differential equation in MATLAB?

The differential equation is: k*r=sqrt( (r`)^2 + r^2 ) The value of k is 2. How can I realize the function and solve it with ode45?
user1839790
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Calculate ODE's with MATLAB

The differential equations: α'(t)=s(β-βα+α-qα^2) β'(t)=(s^-1)(-β-αβ+γ) γ'(t)=w(α-γ) Intitial values α (0) = 30.00 β (0) = 1.000 γ (0) = 30.00 Calculation I want to solve the problem from t_0=0 to t=10 while using the values s = 1, q = 1 and w =…
ErkNis
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