Ventana software support forum

Hi,
How can I formulate time subscript for variables?

For example, how can I define the formula in the attached pic?

In that formula p is variable.

Thank for your attention.

This looks like discrete time notation, and presumably the summation indicates some kind of state variable dynamics. Hard to say how to implement it without knowing what it's for.

Generically, your two choices are to implement it directly using a subscript to represent the elements of j, or to use a stock to represent the dynamics explicitly.

However, since l(t-1) is independent of j in the summation, this simplifies readily:

r(t) = 1/p * p * l(t-1) = l(t-1)

http://metasd.com/2017/11/discrete-time-stinks/

Thanks tomfid,

The correct argument is l(t-j) as shown below:
I want to model a simple lending system as shown below:
In this system, loans are made every year and have a redemption period (p). Although p is constant, I want to change it in different simulation runs.
Every year we must repay 1/p of the principal of each loan until full redemption. In fact, the r(t) is the amount of repayment each year that should be calculated by p and l.

I want to model a simple lending system as shown below:
In this system, loans are made every year and have a redemption period (p). Although p is constant, I want to change it in different simulation runs.
Every year we must repay 1/p of the principal of each loan until full redemption. In fact, the r(t) is the amount of repayment each year that should be calculated by p and l.

How can I formulate time subscript for variables?

For example, how can I define the formula in the attached pic for the loan redemption?

If I'm understanding correctly, all you need is

I've attached a model of a loan. It gets a little messy if you're interested in exact representation of compounding and payment periods, as you can see. This could be quite a bit simpler if you assumed continuous time and payments.