# PDEtoolbox_Error using daeic3 (line 230) Need a better guess y0 for consistent initial conditions.

4 views (last 30 days)
Minjun Bae on 26 Feb 2020
Commented: Minjun Bae on 6 Mar 2020
Hello,
I am trying to solve a system with three partial differential equations coupled by using PDE toolbox.
As I simulate my code, I keep getting an error, saying
Error using daeic3 (line 230)
Need a better guess y0 for consistent initial conditions.
I cannot figure out where the error comes from. Can anyone help me to figure out what the problem is?
Attached PDF file is equations and corresponding code that I am trying to solve.
Any help would be very much appreciated.
Also, let me know if I could provide more information regarding this.

Ravi Kumar on 5 Mar 2020
You do have a singula mass matrix becuase of the equation 2. If I understand correctly equation 1 can be solved in isolation. Once you have u1, can you attempt to solve equation 2 and 3 using u1? This may or may not resolve the issue, it will simplify the system a bit.

Minjun Bae on 5 Mar 2020
Good afternoon,
Thank you so much for the feedback.
My equation 2, which has been modified a little bit, is that
Since state.u(1,:) returns to a matrix with scalar value,
it is my understanding that I cannot use gradient function because it will return 1) gradient wrt x only.
So I defined the equation 2 as below:
(coefficients except f was set to 0)
[[function fmatrix = fcoeffunction(location,state)
.....
fmatrix(2,:) = E_over + I_tkns*(state.ux(1,:).*state.ux(2,:)+state.uy(1,:).*state.uy(2,:))/denom
where denom is defined as
denom = sqrt(state.ux(1,:).^2+state.uy(1,:).^2);]]
I ran the simulation again, and I got the error saying
Error using daeic3, this DEA appears to be of index greater than 1.
I believe that error also comes up when I have a singular matrix (?).
Do you think it is possible for you to identify what the problem is?
Thank you so much for your support.
Ravi Kumar on 5 Mar 2020
Can you attach the complete code that produces the error? Reproduction could would help identify any workaround.
Minjun Bae on 6 Mar 2020
Hello,
Please see the attached pdf file. I have included two function handles as well as my main code.
Thank you so much!
Best regards,