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Re: Differential equation and ode45 or ode15i
Posted:
Jan 27, 2014 2:56 PM


"shatrah " <shatrah1978@gmail.com> wrote in message news:lc63k7$dh3$1@newscl01ah.mathworks.com... > "Torsten" wrote in message <lc5tqg$495$1@newscl01ah.mathworks.com>... >> "shatrah " <shatrah1978@gmail.com> wrote in message >> <lc5sso$kdh$1@newscl01ah.mathworks.com>... >> > "Torsten" wrote in message <lc5r64$o8h$1@newscl01ah.mathworks.com>... >> > > "shatrah " <shatrah1978@gmail.com> wrote in message >> > > <lc5q4c$4a9$1@newscl01ah.mathworks.com>... >> > > > "Torsten" wrote in message >> > > > <lc5mi0$n5t$1@newscl01ah.mathworks.com>... >> > > > > "shatrah " <shatrah1978@gmail.com> wrote in message >> > > > > <lc35in$d3g$1@newscl01ah.mathworks.com>... >> > > > > > dq/dz=dy/dz+q dy/dz=z*y >> > > > > > ds/dz=dy/dz+dq/dz y=10, dy/dz=0 for z=0 >> > > > > > z=15, dz/dz=0 for z=0 >> > > > > > q=11, dq/dz=0 for z=0
*snip*
> Thanks fo reply .... > Please just answe this questin ( my clear one ) Can I use this on matlab > ode45 , dy(1)=dy(2)+d(3) ???? Or must left side contain only dy and right > side don't contain dy ??? Clear question !!! Thanks
For a system like this, use a mass matrix. See the "Mass Matrix and DAE Properties" section on this page:
http://www.mathworks.com/help/matlab/ref/odeset.html
Rewrite your system as:
dq/dz  dy/dz = q dy/dz = z*y  dy/dz  dq/dz + ds/dz = 0
For this system, your mass matrix would be:
[1 1 0; 0 1 0; 1 1 1]
Your f(t, y) would then return [q; z*y; 0], and the solutions would be [dqdz; dydz; dsdz].
 Steve Lord slord@mathworks.com To contact Technical Support use the Contact Us link on http://www.mathworks.com



