InteractionFrequency: Interaction Frequency of a pairwise interaction
In DavidGarciaCallejas/DGC: David Garcia-Callejas' functions

Interaction frequency calculated from net abundances, as a logistic function with an asymptote at the lowest abundance of the two

1	InteractionFrequency(n1, n2, a, x0, threshold)

`n1`	abundance of the first species
`n2`	abundance of the second species
`a`	parameter of the logistic function. A higher a implies faster approach to the asymptote
`x0`	parameter of the logistic function
`threshold`	threshold below which an abundance is considered zero

value, positive and non-integer, of interaction frequency

1 2	InteractionFrequency(n1 = 10, n2 = 100, a = 0.1, x0 = 1, threshold = 1e-5) InteractionFrequency(n1 = 10, n2 = 100, a = 0.01, x0 = 1, threshold = 1e-5)