# How to input the model by linear form?

Hi,guys.I m a freshman of dynare.
Could you please tell me that how can i input the model like “0=cbar(phat+chat)”? that “cbar” means the steady state and the “chat” and “phat” means differences from steady states.
Although the user guide says “repeating a letter for a variable means difference from steady state”.,the matlab tells me “cc” is not defined when i input the model like “0=c*(pp+cc)”.

Hi,

You probably misunderstood the guide, there is no automatic way of constructing difference from steady state variables.

If you linearized your model, you simply need to declare as endogenous the variables representing differences from steady state. If you need to enter the steady state level of some variable in some equation (as your “cbar”), declare it as a parameter, and assign it the true value (possibly as a function of some deep model parameters).

Best,

hi , Sébastien Villemot.

Thank you for your attention.The aim i linearize the model is to find the steady state with the initial value assingned by zero.So does it mean that i have to caculate the steady state value by other means?

by the way ,I have tried your idea and gotten the steady state,but when i make a implus response functions,the matlab told me
??? Error using ==> print_info
MJDGGES returns the following error code10

Error in ==> stoch_simul at 44
print_info(info);

Error in ==> toy1 at 202
info = stoch_simul(var_list_);

Error in ==> dynare at 102
evalin(‘base’,fname) ;

what does these codes mean?My code is
shocks;
var e_z=0.01;
end;

If you want to enter a linearized model into Dynare, then you need to compute the steady state by other means. This can be of course done by Dynare itself, using another MOD file, where you enter the model in nonlinear form. And don’t forget that Dynare is also able to compute the first order approximation of the non-linear model, which is equal to the exact solution of the linearized model.