SPEED Lab iOS Mobile Applications

Mobile iOS Application: Spatial Population Ecological and Epidemiological Dynamics Simulator, Version 2.1

This app is currently available on the iTunes App Store for the iOS platform which runs on Apple's iPhone, iPod Touch, and iPad platforms, and allows users to interactively explore the dynamics of spatial simulation models. Note that this version requires iOS version 5.0 or greater. An Android app will hopefully be available later (when it is, info will be linked to back on the parent Mobile Apps page).

Below is more information about the models included in Version 2.0.1 of the application. Additional models are planned for future versions of the software.

Life: Conway's Game of Life
Vants: Langton's virtual ants
Majority: Majority rule or voter model cellular automaton
DLA: Diffusion-limited aggregation particle model
Cyclic: Generalized "rock paper scissors" in the lattice
SIRS: Spatial epidemiological model.
Dispersal 2: Population model with local dispersal at distance 1 or 2, and long-distance dispersal.
Fragmented Habitat: Population on a landscape with habitat loss and fragmentation
Competitive Species: Two species competing on a landscape with habitat loss and fragmentation
Block Disturbance: Using large-scale disturbance events to control an unwanted species
Vaccinated communities: Epidemiological model with varying vaccination levels among different communities.

User interface

Here is some basic information about the user interface for the application.

Lattice view

You can use pinch-to-zoom with the lattice view to magnify it, and drag the view around if you are zoomed in.
Some models support drawing in the lattice. Tap and hold on the lattice screen, to draw in the lattice. The "brush" menu (under the "more" tab on the iPhone) lets you choose which state/color you are drawing, and the brush size.
Tap the "Save" button to save a snapshot of the image to your device's Photos library.
Tap "Run" to begin the simulation; the "Run" button then becomes a "Pause" button to stop the simulation.
Tap "Reset" to reinitialize the model and start a fresh simulation.
Tap "-" to slow down the simulation, and "+" to speed it up again.
Some models involve populations with heterogeneous habitat, or vaccinations. Tap "cluster" to begin generating a landscape, and "stop" when you are satisfied with the landscape. You can then initialize the population, or tap "reset land" to begin reinitializing the habitat/vaccination.

Plot view

The top row of buttons (Keep, Show All, Hide Old, and Clear Old) let you keep and manage plots of multiple simulation runs within the same figure window. Because the models are stochastic, if you run the same model multiple times, you will see somewhat different results. If you tap "Keep", the current simulation's plot data will be saved. Tapping "Show All" or "Hide Old" determines whether previously Kept plots are displayed. "Clear old" removes all Kept plots.
Tap the "Save" button to save a snapshot of the current plot to your device's Photos library.
The "Run" and other basic model-controlling buttons from the Lattice view are also shown in the Plot view.
"Options" lets you control which things are displayed in the Plot view.

Parameters view

This view displays parameters specific to the current model. Some of the parameters take effect right away (such as birth rates, infection rates, etc.), while others take effect when the model is reset (such as initial infections, etc.).

Settings view

This view (accessed from within the "More" tab on an iPhone) lets you set parameters common to all of the models within the application, such as the size of the lattice, how often to update Plots, etc.

Brush

Here you can control which state will be drawn when you tap-and-hold in the Lattice view, as well as the brush size for drawing.

About

Version and author information. Also, this important acknowledgement of funding: This app is based on work supported by the National Science Foundation under Grant Nos. DMS-0718786 and DMS-0746603 to David Hiebeler.

Known issues/problems

If you press Reset while the model is running, the app may freeze/crash. A workaround for now is that this doesn't seem to happen if you first Pause the model before resetting it. A fix to address this problem has been tested, and is awaiting approval by Apple for release on the App Store. Note that because of the way iOS works, if an app crashes but has not finished crashing and been completely flushed by iOS, if you try to immediately restart the app it appears to hang entirely. This makes the app appear even more buggy. (This issue was mentioned in a review of the app; if you discover bugs in the software, please contact me directly if possible.)