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Topic: Help with ode45
Replies: 3   Last Post: Oct 17, 2012 9:46 AM

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 pietro Posts: 374 Registered: 1/3/09
Re: Help with ode45
Posted: Oct 17, 2012 3:43 AM

"Anna Baturin" <anna_baturin@student.uml.edu> wrote in message <k5ks35\$56m\$1@newscl01ah.mathworks.com>...
> I am trying to use the ode45 function for dy/dx=sin(y*x^2)
> the function was saved as an m file which I called f
> I have to do it for y0=2 and y0=1 and then plot them.
> When I plot I keep getting the error "vectors must be the smae length"
> Here is my work:
> a=-2
> b=2
> y0=2
> y01=1
> [x,y1]=ode45('f',[a,b],y0)
> [x,y2]=ode45('f',[a,b],y01)
> plot(x,y1,'--k',x,y2)
> then I get the error "vectors muct be the smae length"
> How do I fix this?

try this:

function dy = myfun(x,y)
dy = zeros(2,1); % a column vector
dy(1) = y(2);
dy(2) = sin(y*x^2);

[x,y1]=ode45(@myfun,[a,b],y0)

Date Subject Author
10/16/12 Anna Baturin
10/17/12 Torsten
10/17/12 pietro
10/17/12 Steven Lord