{ From user Suresh, Project Fishinapond at Mon, Mar 21, 1994 10:41 AM}
{ System Variables with non-default values: }
Numberwidth := 6
Typechecking := 1
Checking := 1
Saveoptions := 2
Savevalues := 0
{ Non-default Time SysVar value: }
Time := Sequence(0,Num_years_to_iterate,1)
Attribute Reference
Project Fishinapond
Title: Fish in a pond (a dynamic simulation example with chaos)
Description: A dynamic simulation model with chaotic properties. The fish population of this fictional pond is defined as a function of the previous year's population by the expression: population(t)=[1-population(t-1)]*population(t-1)*GrowthFactor where population is a fraction between 0 and 1 and t is time in years. The GrowthFactor reflects a constant condition of the system/environment. If a system has a relatively low growth factor (~2.5) the fish population settles down to a single steady number after a few years. In systems with a higher growth factor (~3.25) the population settles down to two alternating values. Even more volatile systems settle down to 4, 8, 16, etc. alternating values (period doubling). Above a certain threshold (~3.7) the population fails to settle down to any value or set of repeating values (chaos). Different initial populations all settle down to the same values or repeating values in stable systems, while even slightly different initial settings for chaotic systems quickly diverge. The weather is a more common example of an unstable (chaotic) system that is impossible to predict. Slight errors in initial measurements grow exponentially in subsequent calculations of the model.
Author: Suresh
Date: Wed, Feb 23, 1994 12:42 PM
Saveauthor: Suresh
Savedate: Mon, Mar 21, 1994 10:41 AM
Diagstate: 1,40,50,513,270,1
Fileinfo: 0,-2,11516,Project Fishinapond,Fish in a pond
Getresource Pagesetup,1
Chance Num_fish_in_pond
Title: number of fish in a pond
Description: Fish population - represented by a fraction between 0 and 1. Defined in terms of previous year's population and the growth factor (a system constant).~
~
If you're wondering: the icon is supposed to be a sandy pond with little fishies swimming around. There's also a small island with a palm tree in the middle.
