This is a moderately complicated system dynamics model from Hannon & Ruth that shows the motion of an intoxicated person trying to walk in a straight-line north. Every step has a random degree of deviation. The model contains two stocks, x and y representing position. The terms “chosen angle” and “step size” determine motion; consequently there is a tap into x labeled “Moving_x” using the formula step size*cos(chosen angle) and a tap into y labeled “Moving_y” using the formula step size*sin(chosen angle). The chosen angle and step size both employ a Gaussian random variable with the same standard deviation (10*intoxication index), and, respectively, mean=”desired angle” and 1. The “desired angle” is the one that returns the walk along the desired northward path. Some useful features of this model include an interesting first look at changes in x and y, which will be useful for movement functions in later agent based models.
Nova Online: Drunken Random Walk (opens in new tab)
Running this model:
1. Click on the “Capture” button in the tool bar.
2. Click “Load” next to “Capture.”
3. Click “Exec” to run the model through multiple iterations. Click “Stop” to stop the graph.
4. To run the model step by step, click “Capture,” “Load,” “Init,” then “Step.”
from “Intoxication Model” (Fig. 5.3) Dynamic Modeling by Bruce Hannon & Matthias Ruth