a2a: Easily switch between different power law formulations.

In epiphy: Analysis of Plant Disease Epidemics

Easily switch between different power law formulations.

Description

a2a was designed to avoid headaches that are likely to occur when working with different formulations of the binomial power law analysis.

Usage

a2a(x, ...)

## S3 method for class 'numeric'
a2a(
  x,
  slope,
  n,
  from = c("Ai", "ai", "AI", "aI"),
  to = c("Ai", "ai", "AI", "aI"),
  ...
)

## S3 method for class 'list'
a2a(x, to = c("Ai", "ai", "AI", "aI"), ...)

Arguments

x	Intercept parameter to be converted or a named list with the parameter to be converted ("Ai", "ai", "AI" or "aI"), the slope ("slope"), and the number of individual per sampling unit ("n").
...	Additional arguments to be passed to other methods.
slope	Slope parameter.
n	Number of individuals per sampling unit.
from	Kind of the input intercept parameter ("Ai", "ai", "AI" or "aI").
to	Desired kind for the ouput intercept parameter ("Ai", "ai", "AI" or "aI").

Details

The binomial power law can be expressed as: s_y^2 = (intercept)(s_{bin}^2)^b. But different forms of (intercept) are possible depending on the formulation of the binomial power law.

	Ai	ai	AI	aI
Ai	1	n^b	n^(2(b-1))	n^(b-2)
ai	n^(-b)	1	n^(b-2)	n^(-2)
AI	n^(2(1-b))	n^(2-b)	1	n^(-b)
aI	n^(2-b)	n^2	n^b	1

Value

A numeric vector.

Examples

# Values from the power_law() example:
Ai    <- 38.6245
slope <- 1.9356
n     <- 9

# Usual function call syntax:
a2a(Ai, slope, n, from = "Ai", to = "ai")

# Other syntaxes:
inputs <- list(Ai = Ai, slope = slope, n = n)
a2a(inputs, "ai")
require(magrittr)
inputs %>% a2a("ai")

epiphy documentation built on Nov. 16, 2023, 5:06 p.m.