Understanding Particle Diffusion: Analyzing Scatter Plots in MATLAB

[splinewave]

hi all:
i have some insects/particles that i placed in the center of an arena, and tracked their position after a set period of time. what i can get in MATLAB is a 2d scatter plot (several hundred x,y points). i have several different types of particles that show a larger or smaller degree of spread from the center, and have collected their endpoints (i don't have individual trajectories).

can i do something more interesting to communicate just 'how scattered' these particles are after time t? any good tutorials on this given my data (time 1, distance 0; time 2, distance X)? i think i might not be looking for a "diffusion coefficient", since I'm looking at single particles and not concentrations.

i think i might be looking to understand something called a "correlation time".

Thanks for any ideas

 

[Bob S]

When you say 2d scatter plot, do you mean t, r, θ or equivalent (t, x, y)? If you are tracking insects, do you expect any "clumping" meaning natural attractors (social behavior)? Do you have several different simultaneous insect types? Like predator-prey? Measurement of many individual insects is sufficient to get a diffusion coefficient. Sometimes the diffusion coefficient depends on insect concentration (density), like locusts. Locusts begin swarming when a critical density is reached. See

http://www.k8science.org/news/news.cfm?art=2564

Bob S