Talbot

You might think of this as a diffusion/contagion process. We have an r library for this NetdiffuseR

https://cran.r-project.org/web/packages/netdiffuseR/index.html

Empirical statistical analysis, visualization and simulation of diffusion and contagion processes on networks. The package implements algorithms for calculating network diffusion statistics such as transmission
rate, hazard rates, exposure models, network threshold levels, infectiousness (contagion), and susceptibility.

-Tom

**From:** Social Networks Discussion Forum [mailto:[log in to unmask]]
**On Behalf Of **Trotter, Robert T -FS

**Sent:** Tuesday, February 14, 2017 2:05 PM

**To:** [log in to unmask]

**Subject:** Dispersing Insects as Networks: Searching for software that will allow groups of nodes to be treated as a single node

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Greetings! I am new to both social network research, and the SOCNET forum, so a quick introduction seems in order. I am a research ecologist with the USDA, working on evaluating the risks, impacts, and spread associated with non-native
species, I have been using basic graph theory approaches for some of the work I have done, but I am searching for some flexible tools, and I am hoping this community can point me in the right direction.

As a bit of background, I have been modeling the movement of insects among trees on the landscape using variations on very simple rules. As a simple example, imagine a field with one tree on one side of the field which is infested with
insects with an infestation rating of 2 (a severe infestation). Imagine also that there are three trees on the far side of the field which are also infested, each with an infestation rating of 1 (lightly infested). If we assume that the level of the infestation
is a proxy for the age of the infestation, then we would assume that the single tree was infested first, and insects moved from this tree to the other three trees. We can define this using the simple rule: A given tree is infested by receiving insects from
the closest tree which has a higher (and therefore assumed to be older) level of infestation. In this example, we could graphically represent the above by a single dot with three long vectors going to the group of trees on the far side of the field. This
is pretty easy to code, and I have put together some code in MatLab which allows this to be done for tens of thousands of trees. However, biologically, this is not always reasonable.

In the example above, we have assumed that there were three dispersal events, one for each of the three trees on the far side of the field. Biologically however, it is more likely that a single insect crossed the field, and then moved
among the new trees infesting each, with the result being that each was infested at the same time. What I am searching for is software that will allow me to treat the three trees as concurrently infested, so that there is one long vector (across the field),
and then two short vectors, (movement among the trees). I am hoping that someone here can point me in the right direction (vector?) with regards to software. I am familiar with graph theory, but have a (very) limited knowledge of social network analyses
or the terminology associated, so I am also interested in recommendations for a good primer text. Thank you all!

Cheers,

Talbot Trotter

US Forest Service

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