Error using mupadengine/feval (line 187) Invalid equations.
13 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Lada Nuzhna
le 28 Déc 2019
Commenté : Lada Nuzhna
le 1 Jan 2020
I am trying to solve a differential equation, but getting the following error
Error using mupadengine/feval (line 187)
Invalid equations.
My code:
syms r(P);
eqn = diff(r,P,2) == (r^4 / b^2) - (1-k/r)*(r^4/a^2 + r^2);
Dr = diff(r,P);
cond = [ r(0) == 0.1, Dr(0) == 0.1];
rsol(P) = dsolve(eqn ,[0 10], cond);
All the variables used (a,k,b) are defined in the code before.
Will be grateful for any help!
0 commentaires
Réponse acceptée
Jyothis Gireesh
le 31 Déc 2019
I am assuming here that you want the solution to be evaluated over the range [0 10]. But according to MATLAB documentation, the "dsolve()" doesn’t provide the functionality to provide that as an input argument to the function.
I tried running the above code by initializing the values of "a", "b" and "k" with value 1 which didn't yield an explicit solution. In case such a situation arises, it may be better to use numerical integration techniques as ode45. The following code may be useful in case of numerical methods
clear;
syms r(p)
a=2;
b=1;
k=1;
eqn = diff(r,p,2) == r^4/b^2 - (1-k/r)*(r^4/a^2 + r^2);
Dr = diff(r,p);
V = odeToVectorField(eqn);
F = matlabFunction(V, 'vars', {'p','Y'});
rsol = ode45(F,[0 10], [0.1 0.1])
Hope this helps!
Plus de réponses (0)
Voir également
Catégories
En savoir plus sur Applications dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!