Zero constant time

[Monte]

Hi,

My problem is a rate variable computed as level/constant time, where constant time equals zero.
For example, let's consider the following equations:

travel speed (rate)=population (level)/travel time (constant time)

where, travel time=total distance/walking speed

At time=0, people do not walk yet, and thus walking speed equals 0 m/s at t=0, which is mathematically wrong.

I am looking for a solution to this problem. Thank you.

Monte

[Administrator]

In Vensim, I would use the ZIDZ (zero if divide by zero) function.

This is appropriate for the travel time=total distance/walking speed calculation.

No idea if the other SD packages have a function like this, but a simple 'if then else' will work in these instances.

Hope this helps.

Tony.

[Monte]

Dear Tony,

Many thanks for your help.

Monte