How to enter an if...else...end statement for a dae problem

This is my m file:

*M file* function f=ncs1_dae(t,x)

          %Input parameters

          global alpha A AH AI AO AV ACS beta CPH CPI CPIN CPO CPV dB g hB hI hO hH hV Hmax k M MH min Pset qein R rhol rhov ri ro TIN TR vB lambda;

          input()

          %Variables

          TI=x(1);
........
..........

              =x(16);

          %f(1) to f(6) are ODEs

          f(1)=

          f(2)=

          f(3)=

          f(4)=

          f(5)=

          f(6)=

          %f(7) to f(18) are Algebraic Equations

          f(7)=

          f(8)=

          f(9)=

          f(10)=

          f(11)=

          f(12)=

          f(13)=

          f(14)=

          f(15)=

          f(16)=

          f(17)=

          f(18)=

          f=f';

My question is:

I want to enter if....else statements for a few equations...For example, in f(7), if PV<=Pset, mout = 0 else f(7)=. How can I incorporate that. I need to do this for 5-6 equations. Thanks!

[Urvi]

I tried entering an if else statement but when I run the code, it gives me an error saying DAE index appears to be greater than one. Without the if else statement I am getting results. Even though they might be incorrect and some debugging might be needed. What should I understand from this difference?

[Urvi]

Please help! its urgent!

[Jan]

@Urvi: Please read Answers: Why is your question not urgent.

Answer 1

[Azzi Abdelmalek]

 if PV<=Pset
   mout = 0
 else 
   f(7)=mout-alpha*(PV-Pset)
 end

in general

 if condition1
  % action1
 elseif condition2
  % action2

 elseif condtion n
  % action n
 else
  % action n+1
 end

[Urvi]

I have already tried this but I get an error saying "DAE index appears to be greater than 1".

Answer 2

[Jan]

The DAE (or ODE) function must be continuous. Therefore IF, MAX, ABS and time-dependent functions are a big DON'T in functions to be integrated. Use event functions instead.

Remember, that the trajectory of an DAE must be kept on a feasible path. Could this be the case, when you insert a discontinuity?