Stage 4: Visualising the trees in space

Thu, 28/02/2008 - 18:28 — administrator

Step 1	Add two variables inside the tree submodel, and rename them x and y.
Step 2	Enter the following expression for the variable x: rand_const(0,50) We imagine a 1 hectare plot, with the trees on the left-hand side: i.e. their x-coordinate is between 0 and 50 m. The actual x-coordinate for each tree is randomly determined.
Step 3	Enter the following expression for the variable y: rand_const(0,100). The trees can be anywhere between the front and the back of the 1 hectare plot. Hence, the y-coordinate for each tree is randomly determined between 0 and 100 m.
Step 4	Re-build the model.
Step 5	Call up the lollipop display. When it prompts you for the three variables required to set up the display, click on the variable x, the variable y, and the variable size respectively, in that order. You should see a gridded area, with five lollipops on it, representing the five trees created at initialisation time.
Step 6	Run the model again. Now, you can the trees growing, new trees being created, and trees dying off when they reach the threshold height. Note that we have not changed the mathematical nature of the model. All we have done is to change the way we visualise its behaviour — but this has a dramatic effect on our appreciation of what’s going on.

Main menu