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Torsten
Posts:
1,470
Registered:
11/8/10


Re: how to Solve coupled ODEs
Posted:
Feb 7, 2013 3:15 AM


"Henry" wrote in message <keujnd$h64$1@newscl01ah.mathworks.com>... > Hi there, > > I'm having a hard time solving a set of 2 coupled ODEs: > > dx/ds = 1/x * [y* (d + y/s)  a*x*f] > dy/ds = 1/x * [y * (b + y) * f]  y/s  c > > where f = sqrt(x^2 + y^2*(e + y)), and all constants are vectors of (100 x 1). The independent variable is "s". > > % > global a b c d e > y = ode45(@odeeqns, s, [1 1]) > > function dyds = odeeqns(s,y) > global a b c d e > dyds(:,1) = 1./y(1) .*(y(2) .* (d + s ./ y(2))  a .* y(1) .* sqrt(y(1).^2 + (e + y(2)).^2)); > dyds(:,2) =  (y(2) .* (b + y(2)) .* sqrt(y(1).^2 + (e + y(2)).^2))./y(1)  y(2)./s  c; > return > % > > Any help please? > Thanks!
Take a look at example 1 under http://www.mathworks.de/de/help/matlab/ref/ode23.html and you'll recognize the two (or three) errors you made in your small piece of code from above.
Best wishes Torsten.



