# Predetermined variable t+1

Hi,
in my model PPI represents inflation plus one,
in time t-1 there is no price or price=0, so I cannot define inflation for time t (since: PPI=P(t+1)/P(t)) and it starts at time t+1,
now my question is if I should set PPI as predetermined variable? And if not, what should I do about this error?
Thanks for help.

model_diagnostics(M_,options_,oo_)
MODEL_DIAGNOSTICS: The following endogenous variables aren’t present at the current period in the model: PPI
aliye.mod (2.3 KB)

You have no price variable in your model. Price (`P`) should be in the model, and then define

`PPI = P - P(-1);`

Also, `PPI=P(t+1)/P(t)` seems wrong…perhaps you mean `PPI=P/P(t-1)`

When I add price I face the following error:

model_diagnostics(M_,options_,oo_)
MODEL_DIAGNOSTICS: The Jacobian of the static model is singular
MODEL_DIAGNOSTICS: there is 1 colinear relationships between the variables and the equations
Colinear variables:
P
Colinear equations
1 2 4 5 6 7 8 9 10 11 12 14 15
MODEL_DIAGNOSTICS: The singularity seems to be (partly) caused by the presence of a unit root
MODEL_DIAGNOSTICS: as the absolute value of one eigenvalue is in the range of ±1e-6 to 1.
MODEL_DIAGNOSTICS: If the model is actually supposed to feature unit root behavior, such a warning is expected,
MODEL_DIAGNOSTICS: but you should nevertheless check whether there is an additional singularity problem.
MODEL_DIAGNOSTICS: The presence of a singularity problem typically indicates that there is one
MODEL_DIAGNOSTICS: redundant equation entered in the model block, while another non-redundant equation
MODEL_DIAGNOSTICS: is missing. The problem often derives from Walras Law.

And when I do not have it in the model there is no error at all.
aliye.mod (2.3 KB)

See

Thanks a lot for the information.
Now it runs but one of my variables (sp) is nan in final result.
aliye.mod (2.4 KB)

Some of the moments are NaN. But that’s due to `SP` being a constant due to

``````SP=0;
``````

Thank you

I tried to change model to solve sp=0 problem,
Now there is this error, how can I solve this:

model_diagnostics(M_,options_,oo_)
MODEL_DIAGNOSTICS: The Jacobian of the static model is singular
MODEL_DIAGNOSTICS: there is 1 colinear relationships between the variables and the equations
Colinear variables:
T
Colinear equations
1 2
MODEL_DIAGNOSTICS: The presence of a singularity problem typically indicates that there is one
MODEL_DIAGNOSTICS: redundant equation entered in the model block, while another non-redundant equation
MODEL_DIAGNOSTICS: is missing. The problem often derives from Walras Law.

aliye.mod (2.5 KB)

But how can you find `T` if `TSS=0`?

``````TSS=0;
predetermined_variables M, K;
model(linear);
(MSS/PSS)*PPISS*(M(+1)+PPI(+1)-P(+1))-(MSS/PSS)*(M-P)=(TSS/PSS)*(T-P);
``````

It works when `TSS = 2...`

Btw…steady-state values should be derived from the model as a function of the parameters in the model, yeah?. Thus, if they don’t follow an exogenous process. Not sure TSS = 0 was derived from the model.

Yes, I changed the model and not the parameters, but I still think tss=0 is true,
it does not run with tss=2 or other numbers,
I get the following error, does it run for you?

Index exceeds matrix dimensions.
Error in resid (line 101)
if abs(z(i)) < options_.solve_tolf/100
Error in aliye.driver (line 354)
resid;
Error in dynare (line 293)
evalin(‘base’,[fname ‘.driver’]) ;

model_diagnostics(M_,options_,oo_)
MODEL_DIAGNOSTICS: No obvious problems with this mod-file were detected.

aliye.mod (2.5 KB)

Not sure why you have a problem running it…it works for me for TSS=2

All I was saying is that if TSS = 0, then `(TSS/PSS)*(T-P) = 0` in your model. It is the same as replacing `(TSS/PSS)*(T-P)` with 0 in your model…and you can’t find T in that model.

I mean if TSS = 0, try to find T in your model manually, you can’t.

I restarted matlab and problem solved, Thanks so much.

`TSS=0` will imply that `T` drops from the model.

Thank you.