Table 2.

HexSim updater functions. These operators are used within accumulate events to modify accumulator values. Suggestions regarding usage illustrate just one of many possible applications.

Name	Utility
Accumulator Expression	Sets an accumulator equal to an algebraic expression. Standard math operators, accumulators, and global variables may be included.
Accumulator Transfer	Transfesr a quantity from one accumulator into another.
Allocated Hexagons	Returns the number of hexagons in each individual’s allocated area. Useful for quantifying territory sizes.
Births	Returns the number of offspring produced in the most recent reproduction or propagation event.
Clear	Sets an accumulator to zero.
Explored Hexagons	Returns the number of hexagons in each individual’s explored area. Useful for quantifying home range sizes.
Group Size	Returns the number of members present in each individual’s group. Returns zero for floaters.
Group Sum	Sets a target accumulator equal to the sum, taken across all group members, of a specified target accumulator. Useful for ascertaining group composition (e.g. is an alpha-male present).
Hexagon Presence	Detects the presence of nonzero values in a generated hex-map. Useful for triggering premature model termination (e.g. end a disease simulation if the the pathogen disappears).
Increment	Adds a fixed quantity to an accumulator.
Individual ID	Returns each individual’s ID. Useful for simulating DNA recombination in two-sex models.
Individual Locations	Returns the integer ID of the patch each individual is located within, relative to a user-supplied patch-map.
Mate Verification	Sets a mate accumulators to zero if the corresponding mate has died. Assumes the accumulator in question stores mate IDs.
Quantify Environment	Returns the sum or mean of the hexagons in each individual’s explored or allocated area, relative to a specified hex-map. Useful for quantifying resource availability, exposure, population density, and many other quantities of interest.
Quantify Extremes	Similar to the quantify environment updater function, except the minimum or maximum value is returned.
Quantify Location	Returns the floating point score of the hexagon each individual is located within, relative to a user-supplied hex-map.
Resources (Allocated)	Returns the percentage of each individual’s resource target that is presently being met by the hexagons in its allocated area.
Resources (Explored)	Returns the percentage of each individual’s resource target that is presently being met by the hexagons in its explored area. Is also used to simulate resource competition between populations.
Stochastic Increment	Increments an accumulator by an amount drawn from a uniform distribution with user-supplied bounds.
Stochastic Trigger	Returns a 1 with probability p (specified by the user) and a 0 with probability 1-p. A single evaluation is made and then applies to every individual. Used to randomly trigger life history events.
Subpopulation Assign	Randomly selects a user-specified number of individuals from a population, and assigns them a specific accumulator value. Useful for operating on a subset of a population.
Subpopulation Selector	Non-randomly selects a user-specified number of individuals from each group, and sets their target accumulator to 1. Useful for maintaining alpha status in wolf packs after mortality events.
Time Step	Returns the current time step, but includes a modulus operator. Useful as input to data lookup life history events.
Trait Value Index	Returns the index value of probabilistic, genetic, or genetic accumulated traits. Provides a way for individuals to incorporate this trait information into accumulator mathematics or generated hex-map construction.
Uptake	Transfers a quantity from a hex-map into an accumulator. Individual allocated areas define the source region. Useful for modeling the transfer of pathogens from the environment into organisms.