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NetLogo User Community Models(back to the NetLogo User Community Models)
WHAT IS IT?
This is the "Recursive Trees" model from Resnick's "Turtles" book (pp. 110116).
HOW IT WORKS
'turtlesetup' is the main procedure for setting up the one initial turtle. 'drawbranch' is the procedure that is called once per branch segment.
HOW TO USE IT
Click on 'setup' to initialize the model, and then click on 'go' to start execution of the model.
THINGS TO TRY
Be sure to try angleofbranches set to 30, 45, 60, 90, and 120 just to get started. Make initlength as long as you can make it for your screen.
EXTENDING THE MODEL
The 'shrinkfactor' could be a slider to change the 'static' value (0.7) and the 'random' value (0.5, 0.1, and 5). For the 'random' value, I'm guessing that you can start with one value (from 0 to 10); suppose that '2' is chosen. Then the values would be 0.2, 0.1, and 8 (notice that 2 and 8 add up to 10). That would be a good place to start.
NETLOGO FEATURES
This model repeatedly generates new turtles so that there are 2^periods turtles.
RELATED MODELS
If you find this of interest, then you should also look in the Mathematics/ Fractals section of the Models Library.
CREDITS AND REFERENCES
This model is described in Resnick, M. (1994) "Turtles, Termites and Traffic Jams: Explorations in Massively Parallel Microworlds." Cambridge, Ma: MIT Press, pp. 8895. Scott A. Moore (samoore@umich.edu) of the University of Michigan Business School adapted this model to NetLogo. 
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