ode45
in [Matlab]
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From: Rady on 5 Aug 2010 12:52 Hello, I am using ode45 to solve a system of dfq's, and the problem is that it takes too long and the data is not plotted, and I know there is data. What can resolve that? Thank you
From: Steven_Lord on 5 Aug 2010 16:17 "Rady " <bergen310(a)hotmail.com> wrote in message news:i3eq7k$9fn$1(a)fred.mathworks.com... > Hello, > I am using ode45 to solve a system of dfq's, and the problem is that it > takes too long and the data is not plotted, and I know there is data. What > can resolve that? > > Thank you Try a stiffer solver. http://www.mathworks.com/company/newsletters/news_notes/clevescorner/may03_cleve.html -- Steve Lord slord(a)mathworks.com comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ To contact Technical Support use the Contact Us link on http://www.mathworks.com
From: Rady on 5 Aug 2010 20:16 "Steven_Lord" <slord(a)mathworks.com> wrote in message <i3f699$7kh$1(a)fred.mathworks.com>... > > > "Rady " <bergen310(a)hotmail.com> wrote in message > news:i3eq7k$9fn$1(a)fred.mathworks.com... > > Hello, > > I am using ode45 to solve a system of dfq's, and the problem is that it > > takes too long and the data is not plotted, and I know there is data. What > > can resolve that? > > > > Thank you > > Try a stiffer solver. > > http://www.mathworks.com/company/newsletters/news_notes/clevescorner/may03_cleve.html > > -- > Steve Lord > slord(a)mathworks.com > comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ > To contact Technical Support use the Contact Us link on > http://www.mathworks.com Hello, thank you for the response. I tried ode23s, and now I get a lot of error codes... Here it is, any help would be greatly appreciated: Error Code: ??? In an assignment A(I) = B, the number of elements in B and I must be the same. Error in ==> react at 30 dydt1(3)=k*cos(A3).*C+y1*(A1.^2+A2.^2); Error in ==> odearguments at 110 f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0. Error in ==> ode23s at 188 [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ... Error in ==> dydt1 at 6 [t,y]=ode23s('react', tspan ,x0); Why would that be? The original code is: tspan=linspace(0,1,0.0003); x0=[0 0 0]; [t,y]=ode23s('react', tspan ,x0); Thank you
From: Torsten Hennig on 5 Aug 2010 22:38 > "Steven_Lord" <slord(a)mathworks.com> wrote in message > <i3f699$7kh$1(a)fred.mathworks.com>... > > > > > > "Rady " <bergen310(a)hotmail.com> wrote in message > > news:i3eq7k$9fn$1(a)fred.mathworks.com... > > > Hello, > > > I am using ode45 to solve a system of dfq's, and > the problem is that it > > > takes too long and the data is not plotted, and I > know there is data. What > > > can resolve that? > > > > > > Thank you > > > > Try a stiffer solver. > > > > > http://www.mathworks.com/company/newsletters/news_note > s/clevescorner/may03_cleve.html > > > > -- > > Steve Lord > > slord(a)mathworks.com > > comp.soft-sys.matlab (CSSM) FAQ: > http://matlabwiki.mathworks.com/MATLAB_FAQ > > To contact Technical Support use the Contact Us > link on > > http://www.mathworks.com > > > > Hello, thank you for the response. I tried ode23s, > and now I get a lot of error codes... > Here it is, any help would be greatly appreciated: > Error Code: > ??? In an assignment A(I) = B, the number of > elements in B and > I must be the same. > > Error in ==> react at 30 > dydt1(3)=k*cos(A3).*C+y1*(A1.^2+A2.^2); > > Error in ==> odearguments at 110 > f0 = feval(ode,t0,y0,args{:}); % ODE15I sets > args{1} to yp0. > > Error in ==> ode23s at 188 > [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, > odeArgs, odeFcn, ... > > Error in ==> dydt1 at 6 > [t,y]=ode23s('react', tspan ,x0); > > Why would that be? > > The original code is: > tspan=linspace(0,1,0.0003); > x0=[0 0 0]; > [t,y]=ode23s('react', tspan ,x0); > > Thank you And where do we find 'react' ? Best wishes Torsten.
From: Rady on 6 Aug 2010 12:50
Here is react.m Hope you can help function dydt1 = react (t,y) y1=6; k=2; L=1; z=0:0.00011999:1; t=z/L; c=0:0.0003:2.5; a=4*k; s=y1/a; m=1./(1+(s.*c).^2).^0.5; cons=((2.*k)./m); [sn0,cn0,dn0]=ellipj(cons,m); t(8335)=[]; A1=(c.*((dn0.*(t-1)+1)./(2.*dn0.*(t-1)))).^0.5; A2=(c.*((1-dn0.*(t-1))./(2.*dn0.*(t-1)))).^0.5; psi=0:0.0003:2.5; % dydt1 = zeros(size(y)); % disp (size(dydt1)) % size(A1) % size(A2) C=(A2./A1)+(A1./A2); R=(A1.^2+A2.^2); % A1=y(1); % A2=y(2); % psi=y(3); % dydt1(1)=k*A2.*sin(psi); % dydt1(2)=k*A1.*sin(psi); % dydt1(3)=k.*cos(psi).*C+y1.*R; dydt1=[(k*A2.*sin(psi)).';(k*A1.*sin(psi)).';(k.*cos(psi).*C+y1.*R).']; disp(dydt1) |