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shatrah
Posts:
11
Registered:
1/26/14
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Re: Differential equation and ode45 or ode15i
Posted:
Jan 27, 2014 10:25 PM
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"Steven Lord" <Steven_Lord@mathworks.com> wrote in message <lc6dl9$mlf$1@newscl01ah.mathworks.com>... > > "shatrah " <shatrah1978@gmail.com> wrote in message > news:lc63k7$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 > your answer on ode15i but my question on ode45 ? > *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
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