Not a Lotka-Volterra figure

I'm trying to do the Lotka-Volterra model (this website) in Vissim. Here I attached the Vissim file "Lotka_Volterra.vsm". However, I cannot reproduce the cyclic pattern (left pannel below). Instead, my figure seems not convergent (right panel below). I have decreased my time step into 0.001, but it didn't help. Could someone tell me how to fix it?

Lotka_Volterra.vsm

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pdarnell

Hi Tom. The problem is that you have limited the plot point count to only 120, but given your bounds of 0-1000 and step size of .001, you will need 1e6 points to see smooth plots. You are essentially plotting random numbers.

I have attached a diagram with sliders for input in autorestart mode to allow you to explore the solution space, and set the max points to 0 which will give you unlimited plot data points. The coefficients are set to the baboon/cheetah example in wikipedia [https://en.wikipedia.org/wiki/Lotka–Volterra_equations] and show good agreement. I also included an XY plot to explore the phase space of the predator prey model.

Lotka_Volterrav2.vsm

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pdarnell

Lotka_Volterrav2.vsm

Tom_abc

Hi Tom. The problem is that you have limited the plot point count to only 120, but given your bounds of 0-1000 and step size of .001, you will need 1e6 points to see smooth plots. You are essentially plotting random numbers.

I have attached a diagram with sliders for input in autorestart mode to allow you to explore the solution space, and set the max points to 0 which will give you unlimited plot data points. The coefficients are set to the baboon/cheetah example in wikipedia [https://en.wikipedia.org/wiki/Lotka–Volterra_equations] and show good agreement. I also included an XY plot to explore the phase space of the predator prey model.

Thanks Pete! Now I can reproduce these figures. Your inclusions of sliders and XY plot are also very helpful!

Ric_22025

Tom,

Just a note about your model, in the topmost "label" block where you have written the hyperlink, you can make it into an actual hyperlink by setting two additional "label" properties shown below in red;

Ric