I have a set of second order differential nonlinear equation and I want to solve them together with ode45, how could I write codes for them?or better to say I want to define state transition function for such equations.
2 Ansichten (letzte 30 Tage)
Ältere Kommentare anzeigen
roya afshar
am 15 Dez. 2018
Kommentiert: madhan ravi
am 17 Dez. 2018
first three equations all variable and constants are not in vector or matrix form but 4th equation is a 3by1 vector like this:
x''=y'+y+x-(x)/(x^2+y^2+z^2)^1.5+1
y''=x'-x+y-y/(x^2+y^2+z^2)^1.5
z''=-z/(x^2+y^2+z^2)^1.5
m''=[x'' y'' z'']'+[1 2 3]
and I want to write function for this system like this function that i have found in one of matlab example:
function dxdt = vdpStateFcnContinuous(x)
%vdpStateFcnContinuous Evaluate the van der Pol ODEs for mu = 1
dxdt = [x(2); (1-x(1)^2)*x(2)-x(1)];
end
2 Kommentare
Akzeptierte Antwort
madhan ravi
am 17 Dez. 2018
I believe :
[t,x]=ode45(@eqns,[0 10],[1;0;0;0;0;0;0;0;0;0;0;0]); % function call
plot(t,x(:,1)) % to plot the solution
function dxdt = eqns(t,x) % function definition
dxdt = [x(2);
x(4)+x(5)+x(1)-(x(1)/((x(1)^2+x(3)^2+x(5)^2)^1.5))+1;
x(4);
x(2)-x(1)+x(3)-(x(3)/((x(1)^2+x(3)^2+x(5)^2)^1.5));
x(6);
-x(5)/((x(1)^2+x(3)^2+x(5)^2)^1.5);
x(2:2:6);
[x(4)+x(5)+x(1)-(x(1)/((x(1)^2+x(3)^2+x(5)^2)^1.5))+1;x(2)-x(1)+x(3)-(x(3)/((x(1)^2+x(3)^2+x(5)^2)^1.5));-x(5)/((x(1)^2+x(3)^2+x(5)^2)^1.5)]+[1;2;3]];
end
2 Kommentare
Weitere Antworten (1)
Siehe auch
Kategorien
Mehr zu Function Creation finden Sie in Help Center und File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!