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From: Pawel on 25 Jun 2010 06:20
I have got following code:

y=dsolve('Dy=y*(1-y/5)','y(0)=6','x');
solution=inline(vectorize(y),'x');
x=0:0.01:10;
plot(x,solution(x));

It is the logistic equation which is plotted well. However If I change the code to:

y=dsolve('Dy=y*(1-y/5)+sin(x)','y(0)=6','x');
solution=inline(vectorize(y),'x');
x=0:0.01:10;
plot(x,solution(x));

I got an error saying:

??? Error using ==> inlineeval at 15
Error in inline expression ==> matrix([])
Undefined function or method 'matrix' for input arguments of type 'double'.

Error in ==> inline.subsref at 27
INLINE_OUT_ = inlineeval(INLINE_INPUTS_, INLINE_OBJ_.inputExpr, INLINE_OBJ_.expr);

Please, help me sort it out :)

Thank you in advance for hour help and time .

Pawel
From: Steven Lord on 25 Jun 2010 09:46

"Pawel " <pc504(a)live.mdx.ac.uk> wrote in message
news:i01vss$h2a$1(a)fred.mathworks.com...
>I have got following code:
>
> y=dsolve('Dy=y*(1-y/5)','y(0)=6','x');
> solution=inline(vectorize(y),'x');

Don't do this. Just use SUBS to substitute in values to obtain results you
can PLOT, or EZPLOT the symbolic solution.

> x=0:0.01:10;
> plot(x,solution(x));
>
> It is the logistic equation which is plotted well. However If I change the
> code to:
>
> y=dsolve('Dy=y*(1-y/5)+sin(x)','y(0)=6','x');

When you execute this line, you should see a warning that indicates that
MATLAB could not find an explicit solution. Therefore evaluating the
(empty) solution will not work. Instead, solve the ODE numerically using
ODE45 or one of the other numeric ODE solvers.

*snip*

--
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


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