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Questions tagged [ode45]

140 questions
7
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Imitate ode45 function from MATLAB in Python

I am wondering how to export MATLAB function ode45 to python. According to the documentation is should be as follows: MATLAB: [t,y]=ode45(@vdp1,[0 20],[2 0]); Python: import numpy as np def vdp1(t,y): dydt=…
Migui Mag
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ODE Times Matlab vs R

If using a variable time step solver such as ODE45 in matlab - I would define a time span for the outputs, i.e. times = [0 50], and matlab would return results at various time steps between 0 and 50. However in R it appears I have to define the…
Sarah Halliday
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ode45 for Langevin equation

I have a question about the use of Matlab to compute solution of stochastic differentials equations. The equations are the 2.2a,b, page 3, in this paper (PDF). My professor suggested using ode45 with a small time step, but the results do not match…
GMV871
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Solving 7 equations of first order equations ode45 Matlab

I am trying to solve a system with seven differential equations. And I am having a hard time grapsing the ode45 solver. These are the equations: ω2_dot = -0.75 ω1 ω3 ω1_dot = 0.75 ω2 ω3 + 0.2 ω3_dot = 0 q1_dot = 1/2(ω1q4 + ω2q3 - ω3q2) q2_dot =…
SHiSA
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1 answer

Passing matrices as input in scipy.integrate.solve_ivp python

I was solving a 2DOF spring-mass-damper system given below: These are the 2 governing Equations I have solved it in the following way: from scipy.integrate import solve_ivp import numpy as np import matplotlib.pyplot as plt m1 = 3 m2 = 5 k1 =…
user15014634
2
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1 answer

Matlab - ode45 - Unable to meet integration tolerances without reducing the step size below the smallest value allowed (1.136868e-13) at time t.

I am programing a mathematical model from an article about angiogensis but when I try to plot the functions with the given parameteres and initial values, the program doesn't run for the entirety of the timespan I defined, showing a part of the…
Maria Enes
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Solving a system of ODEs using ODE45

I am trying to learn how to use MATLAB to solve a system of differential equations (Lorenz equations) and plot each solution as a function of t X’ = −σx + σy Y’ = ρx − y − xz Z’ = −βz + xy where σ = 10, β = 8/3, and ρ = 28, as well as x(0) = −8,…
Tina
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Using @ or '' for ode45 in Matlab?

I am a little confused as to when to use ode45(@functionname, tspan, initialvalues,...) or ode45('functionname', tspan, initial values,...). I have seen examples using both but sometimes one works and the other doesn't. e.g. [t,y]=ode45(@MM2,…
Richard
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1 answer

Input matrix to function file of ode45

I have a code(which requires a lot input be given by the user) which will give me a n x n matrix(say A), which I have to use to solve a system of ODEs X'=AX. How do I include this matrix A in the function file(.m file) of ode45. If I include the…
Rhinocerotidae
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Matlab: Differential equation (ode45): Can I reverse tspan for better initial conditions?

I'm using ode45 to solve/plot a second-order differential equation in Matlab. My tspan is from 0 to 0.25. But the initial conditions near zero are ill-defined (slope goes to infinity, complex values). The conditions near 0.25 are well defined (both…
Ribbon Cable
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Matlab ode45 vs. ode23, different solutions

I used ode45 and ode23 for a set of non-stiff differential equations. However, both methods converge to a slightly different solution. How can I find out which one is correct? See attached plot where blue is ode45, red is ode23. The dashed lines are…
Jurriën
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Matlab - ODE45 - change the number of time steps

I have a function with the handle @func with initial condition y0 that I want to test over t = [0, tspan]. What, exactly, do I need to do to increase the number of time steps ode45 uses, without changing tspan? I saw the MATLAB documentation of…
farid99
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Matlab → R, lost in translation: why ode45 yields totally different results?

I am neither very familliar with coding nor stackoverflow, I am trying to replicate this following work: https://doi.org/10.1007/978-1-0716-0191-4_12 using the data provided in the book chapter. I do not have access to MATLAB, I tried to run the…
Strack
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How to correctly set the 'rtol' and 'atol' in scipy integration module 'solve_ivp' for solving a system of ODE with unknown analytic solution?

I was trying to reproduce some results of ode45 solver in Python using solve_ivp. Though all parameters, initial conditions, step size, and 'atol' and 'rtol' (which are 1e-6 and 1e-3) are same, I am getting different solutions. Both of the solutions…
Rebeka Sarkar
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Solving a 4 ODE system in MATLAB using ode45

I am not very used to MATLAB and I'm trying to solve the following problem using MATLAB ode45, however, it's not working. I was working on a problem in reaction engineering, using a Semi-Batch Reactor. The reaction is given by A + B ---> C + D A is…
Charbel Nicolas
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