Hello friends

How to write a function that is dependent on time in the DYNARE.

Like x=1+exp(k *t)_2exp(h* t)

I want friends to help me in this case.

Thanks

Hello friends

How to write a function that is dependent on time in the DYNARE.

Like x=1+exp(k *t)_2exp(h* t)

I want friends to help me in this case.

Thanks

Hi, I do not know why you would need that… But if you do not rely on the perturbation approach (and use a perfect foresight based solution method) you can simply add a state variable named `time`

with corresponding equation:

```
time = time(-1) + 1;
```

in the `model`

block. If you set the initial condition of this new variable to zero, you will have exactly what you want.

Best,

Stéphane.

thanks for the reply

Now I encountered the following error

Residuals of the static equations:

Equation number 14 : -1

Hi, This equation (random walk with drift) does not admit any steady state. That is expected. Do you really need a steady state?

Best,

Stéphane.

Hi, Stepan

I also know that this equation does not admit any steady state.

But anyway, I encounter this error and can not continue to work.

I want to write the following equation in the DYNARE, but I do not know how.

Best

esmael

Hi Esmael,

I do not really understand your equation (the term between square brackets looks like the solution of a linear second order differential equation), but in this case you do not need to declare t as a variable to have this equation in Dynare. Suppose you have a term like e^{\alpha t }, where \alpha is a parameter. Then you have:

e^{\alpha (t+1)} = e^{\alpha t}e^{\alpha}

Hence it is possible to define this term recursively. Let A_t = e^{\alpha t}, you must have A_{t} = e^{\alpha}A_{t-1} , and you would write something like:

```
A = exp(alpha) * A(-1);
```

in you model block. The steady state of this equation is well defined (A=0), and this steady state is stable provided \alpha<0.

Best,

Stéphane.