Transcript Random

RANDOM BUILTIN FUNCTION IN
STELLA
RANDOM(<min>, <max>, [<seed>])
The RANDOM builtin generates a series of uniformly
distributed random numbers between min and max.
RANDOM samples a new random number in each
iteration of a model run.
If you wish to replicate the stream of random
numbers, specify seed as an integer between 1 and
32767.
To replicate a simulation, all entities that use
statistical functions must have seeds specified. Each
entity using a statistical function should use a
separate seed value.
Examples:
RANDOM(0,1) creates a non-replicable
uniformly distributed stream of numbers
between 0 and 1.
RANDOM(0,1,147) creates a replicable
uniformly distributed stream of numbers
between 0 and 1.
RANDOM(0,10,12) gives a replicable
uniformly distributed stream of numbers
between 0 and 10.
RANDOM(10,13,12) gives a replicable
uniformly distributed stream of numbers
between 10 and 13.
Build the flower model of Chapter 6 to reproduce
the output shown on the next page.
Or get it from
http://www.atmosedu.com/WSU/esrp310-550/PP/Flowers.STM
Now add a new converter for temperature and connect it
To the intrinsic growth rate. In the original model the
intrinsic growth rate was fixed at 1.0. Here we’ll let
Temperature be Random (20,30,999)
and intrinsic growth rate = temperature/25.0
We added the seed here so all simulations will look the same.
Paste your resulting graphs of
Flower area, growth, and decay here.
Try letting Temperature be Random
(15,35,999)
and intrinsic growth rate =
temperature/25.0
What do you expect to be different for this
new simulation?
ANSWER
Paste your resulting graphs of
Flower area, growth, and decay here.
NORMAL(<mean>,<std>, [<seed>])
The NORMAL builtin generates a series of normally
distributed random numbers with a specified mean and std
(standard deviation).
NORMAL samples a new random number in each iteration
of a simulation.
If you wish to replicate the stream of random numbers,
specify seed as an integer between 1 and 32767. To
replicate a simulation, all entities that use statistical
functions must have seeds specified. Each entity using a
statistical function should use a separate seed value.
Examples:
NORMAL(0,1) gives a non-replicable normally distributed
stream of numbers (mean=0, standard deviation=1)
NORMAL(0,1,147) gives a replicable normally distributed
stream of numbers (mean=0, standard deviation=1)
NORMAL(5,1,12) gives a replicable normally distributed
stream of numbers (mean=5, standard deviation=1)
NORMAL(10,5,102) gives a replicable normally distributed
stream of numbers (mean=10, standard deviation=5)
Now let Temperature be Normal (25,5,999)
and intrinsic growth rate = temperature/25.0
We added the seed here so all simulations will look the same
and make it easier for your instructor to see if you got things
set correctly.
Paste your resulting graphs of
Flower area, growth, and decay here.
Now let Temperature be Normal (25,10,999)
and intrinsic growth rate = temperature/25.0
What do you expect to be different for this new simulation?
ANSWER
Paste your resulting graphs of
Flower area, growth, and decay here.
Download the 3rd version of the MonoLake Model.
http://www.atmosedu.com/WSU/esrp310-550/monoLake/MonoLake3.STM
This has a comparitive graph set for volume in the lake.
Run the model once to get a graph of water in the lake
with a fixed export of 100.
Now run with export set to Normal (100,50,999) . Run this
7 times.(don’t expect big things here)
Now run with export set to Normal (100,50) . Run this 7
times
Paste your resulting graphs of
Flower area, growth, and decay here.
Comment on the advantages and
disadvantage of the seed