the math of delays

Barry · Post by **Barry** » Tue Oct 30, 2007 2:54 pm

What's the easiest math way to show a delay? I'm still learning some basics.

I saw simply dividing by, say 3...on a quality/perceived quality model...and it gave a line that slowly approached making perceived and actual quality meet. But the math doesn't work....like 3 days later it isn't the number that arrived 3 days ago. I also tried the built in delay on ithink (one of which just lets the numbers arrive later in time), and I got an overshoot and undershoot graph. Maybe that's right, but seems like I'm missing something very basic.

Post by **tomfid** » Tue Oct 30, 2007 4:22 pm

You might check out Chapter 5 of the Road Maps series, which includes 2 articles on delays. http://sysdyn.clexchange.org/road-maps/rm-toc.html

malli · Post by **malli** » Wed Oct 31, 2007 2:45 pm

I do not know which version of Ithink you are using. But the DELAY function in ithink is an infinite order (pipeline) delay. The title is misleading.

In IThink (atleast on versions 9.0 and below) you have to make the delay structure manually and not use the inbuilt macro for the continuous delays which are normally used in SD.

You might want to start of with Sterman's book "Business Dynamics - Systems Thinking & Modeling for a Complex World", work through the initial chapters, and then move on to chapter 11 - which is on delays

Regards
Malli

Barry · Post by **Barry** » Tue Nov 27, 2007 2:58 am

Thanks. That book helped. It answered questions that I've had since day 1.