Solving 3 simultaneous first order differential equations

If none of the variables s, p, x depend on µ you can simply go ahead and solve the three differential equations. Once solved you can get µ as a function of time by plugging in s(t) and p(t) in the first equation.

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Abhivyakti 2013-12-29

Hey

I have resolved the recursion error. The problem is, that my program doesn't seem to work.

This is what I have used :

function dydt=react(t,y) dydt=zeros(3,1);

um=0.71; ks=37.72; sm=510; kp=160.83; a=0.81; yxs=0.03; ms=0.0011; k1=33.04; k2=0.0001;

y=zeros(3,1); x=y(1); s=y(2); p=y(3);

dx=(um*(s/(s+ks))*((1-(s/sm))^a)*(kp/(kp+p)))*x; ds=-1*((um/yxs)*(s/(s+ks))*((1-(s/sm))^a)*(kp/(kp+p)) + ms)*x; dp=(k1*(um*(s/(s+ks))*((1-(s/sm))^a)*(kp/(kp+p)))+k2)*x; dydt=[dx;ds;dp];

I give the following command:

[T,Y]=ode45('react',[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15],[0.2 100 0.2]);

In the output Y, I am just getting the initial values of the three variables i.e x,s &p, for each corresponding value of time.

i.e

y= 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000 0.200000000000000 100 0.200000000000000

What am i doing wrong here?

Ranganatha B R 2019-6-5

If you remove that you will get an error as to y is not defined. You cannot have an expression called y(1)

Torsten 2019-6-5

编辑：Torsten 2019-6-5

y is one of the inputs for function "react". Thus there will be no error removing "y=zeros(3,1)".

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Solving 3 simultaneous first order differential equations

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Solving 3 simultaneous first order differential equations

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