modelling biological & physical systems simon lynch [email protected]
TRANSCRIPT
modelling biological & physical systems
Simon Lynch [email protected]
biological systems
• simple (eg: cell growth)• swarming & flocking• evolution• ecosystems
physical systems
examples...• atomic (sub-molecular) small &
fast
• molecular (fluid particles, etc)• erosion big & slow
• continental movement• weather systems lots to
• climate change model
moths, fires, etc
the problem
complexity #1 – scale
• spatial - too big or too small• temporal - too fast or too slow• logical - too many objects /
parts
the problem
complexity #2 – interactivity
• lots of interaction between parts
• lots of interdependence between parts
• emergent behavioureg: cellular automata
computational modelling
• spreadsheets, etc?ok for some v.simple systems but – no observation
• programming languagesok but – big effort needed (& lots of time)
• special modelling toolseg: NetLogo (ccl.northwestern.edu/netlogo/)good & quick but some limitations
sample NetLogo codeto move-thru-field ;; turtle procedure
ifelse (light-level <= ( 1 / (10 * sensitivity) ))
[ ;; if there is no detectable light move randomly
rt flutter-amount 45 ]
[ ifelse (random 25 = 0)
;; add some additional randomness to movement
[ rt flutter-amount 60 ]
[ ;; turn toward the brightest light
maximize
;; if light ahead below sensitivity threshold
;; head to it otherwise move randomly
ifelse ( [light-level] of patch-ahead 1 / light-level
> ( 1 + 1 / (10 * sensitivity) ) )
[ lt ( direction * turn-angle ) ]
[ rt flutter-amount 60 ]
]]
if not can-move? 1
[ maximize ]
fd 1
end
from NetLogo sample model library"Moths" model